14.2g mass of sodium phosphate would have to be added to 2.0l of this solution to completely eliminate the hard water ions.
To solve this question we need to find the moles of Ca2+ and Mg2+ ions. And based on the reactions: 3Ca2+ + 2PO4 Ca(PO4)2 (S)
3Mg2+ + 2PO42 → Mg3(PO4)2 (S)
we can find the moles of phosphate required to precipitate all these ions and its mass: Moles Ca2+1.OL* (0.055mol/L) = 0.055mol ,Moles Mg2+: 1.OL * (0.075mol/L) = 0.075mol
Total moles = 0.13 moles of ions, Moles of phosphate ion required: 0.13 moles (2 moles PO,3 moles ions) = 0.0867 moles PO43-
The moles of sodium phosphate (Na3PO4) are =
0.0867 moles. The mass is -Molar mass Na3PO4: 164g/mol-:0.0867 moles Na3PO4* (164g/mol) =
14.2g of sodium phosphate are required
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A buffer solution is prepared that is 0.18 M NH3 and 0.27 M NH4Cl. What is the pH of this buffer? Kb for NH3 is 1.8 x 10-5
The correct answer is: 9.08
Can someone explain how to do this for me?
The pH of acid is between 0-7 on pH scale while for base pH range is from 7-14. Therefore, the pH of this buffer is 5.14. pH is a unitless quantity.
What is pH?pH is a measurement of amount of hydronium ion H₃O⁺ in a given sample. More the value of hydronium ion concentration, more will be the solution acidic.
On subtracting pH from 14, we get pOH which measures the concentration of hydroxide ion in a given solution. pH depend on the temperature. At room temperature pH scale is between 0 to 14. pH of neutral solution is 7.
0.18 M =NH₃
0.27 M= NH₄Cl.
Kb of NH₃ = 1.8 × 10⁻⁵
pKb = - log (kb)
= - log (1.8 × 10⁻⁵)
= 4.74
Using Henderson equation
pH = Pkb +ln [ NH₄Cl ]/ [NH₃]
= 4.74 + ln (0.27 /0.18)
= 5.14
Therefore, the pH of this buffer is 5.14.
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consider the following oxides: so2so2 , y2o3y2o3 , mgomgo , cl2ocl2o , and n2o5n2o5 . how many are expected to form acidic solutions in water?
Nonmetal oxides form acid solutions. SO2, Cl2O, and N2O5 are acid solutions.
A chemical that offers off hydrogen ions in water and paperwork salts through combining with positive metals. Acids have a sour flavor and turn positive dyes purple. a few acids made by using the body, such as gastric acid, can assist organs work the way they must. An example of an acid is hydrochloric acid.
An acidic solution has a high attention of hydrogen ions, H +start superscript, plus, stop superscript, greater than that of pure water. An acidic solution is a liquid combination that happens when hydrogen ions are launched while mixed with water. This definition is known as the Brønsted-Lowry theory: acids provide hydrogen protons, at the same time as bases "accept" hydrogen protons. some answers are more acidic than others.
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based on their structures, rank phenol, benzene, benzaldehyde, and benzoic acid in terms of lowest to highest boiling point. explain your reasoning.
Increasing order of boiling point of the given molecules is
Benzene< Benzaldehyde<Phenol<Benzoic acid.
Boiling point is directly proportional to intermolecular forces.
The intermolecular forces present in the given molecules are.
so, as benzene is nonpolar , only weak london dispersion force is present. Hence boiling point of benzene is least among the given molecules. Benzaldehyde is polar, so dipole -dipole force is also present. But no H-bonding is present. Hence, boiling point of benzaldehyde is less than that of phenol and benzoic acid. Now, both phenol and benzoic acid is polar as well as they can form H-bonding. But phenol can only form intermolecular hydrogen bonding, but benzoic acid can form both intermolecular as well as intramolecular H bonding. So it can exist as dimer. The presence of dimer further strengthen the vander Waals dispersion forces , that increases the boiling point of Benzoic acid.
Hence increasing order of boiling point of the given molecules is
Benzene< Benzaldehyde<Phenol<Benzoic acid.
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If an atom, such as hydrogen, is able to form a covalent bond, describe what happens when the
electron shells of two atoms overlap?
The potential energy between the nuclei is minimized and the orbital shells overlap.
What is a covalent bond?We know that a covalent bond is the kind of bond that is formed when there is the combination of two atoms when there is the overlap of the orbitals of the two atoms. In the case of the hydrogen atoms, we can say that there is a bond as we notice that the two atomic orbitals have become overlapped on each other.
Let us note that when the two atoms are still far from each other, the potential energy between the atoms is high and as such the atoms of the element would tend to repel each other.
As the two atoms begin to approach each other, the repulsion between the nuclei of the elements is seen to become minimized and the bond is now seen to be formed as the atomic orbitals become overlapped.
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which list contains only strong acids? (5 points) a. hcl, hno3, hf, hclo4 b. h2so4, h3po4, hclo4, nh3 c. hno3, h2so4, naoh, h3po4 d. hcl, hno3, h3po4, hclo4 e. hcl, h2so4, hclo4, hi
a. hcl, hno3, hf, hclo4 b. h2so4 list contains only strong acids.
Chloric acid, hydrochloric acid, hydrochloric acid, hydroiodic acid, nitric acid, perchloric acid, and sulfuric acid are the 7 main acids. These are strong acids since they can completely dissociate in water. A strong acid is described as an acetone that completely disintegrates when added to water. Because the hydrochloric acid inside the preceding example donates every one of its protons to the remedy and totally dissolves, it is classified as a strong acid.
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calculate the volume in liters of a mm silver(ii) oxide solution that contains of silver(ii) oxide . round your answer to significant digits.
The volume of the solution is 1.84 × [tex]10^{4}[/tex] L.
The formula used to get the molarity of the solution is used to determine the volume of the solution:
Molarity= [tex]\frac{Mass of the solute}{molar mass of solute * Volume of solution(in L)}[/tex]
We are given:
Molarity of solution = 8.75 × [tex]10^{-5}[/tex] M
Given the mass of silver (II) oxide = 200 g
Molar mass of silver (II) oxide = 124 g/mol
Put the values in the formula:
8.75 × [tex]10^{-5}[/tex][tex]10^{-5}[/tex] = [tex]\frac{200}{124* Volume}[/tex]
Volume= 1.84 × [tex]10^{4}[/tex] M
A chemical species' concentration in a solution, specifically the amount of a solute per unit volume of solution, is measured by its molar concentration. The most used molarity unit in chemistry is the number of moles per liter, denoted by the unit symbol mol/L or mol/dm3 in SI units.
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which of the following is false about crystal field theory? group of answer choices weak field ligands absorb purple light. the color of a coordination compound is the color of light absorbed.
The following statement is false about crystal field theory : the color of a coordination compound is the color of light absorbed.
Crystal field theory (CFT) describes how a static electric field produced by a surrounding charge distribution breaks degeneracies of electron orbital states, usually d or f orbitals (anion neighbours).
Hans Bethe, a physicist, developed the crystal field theory (CFT) for crystalline solids in 1929.
The following is how Crystal Field Theory explains the colors of coordination compounds: The splitting of a d-orbital into multiple orbitals is known as crystal field splitting. When white light strikes the compound, an electron moves into a higher state, absorbing a specific wavelength of light.
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Draw the Lewis structure for PF3Cl2 in the window below and then answer the questions that follow. What is the electron-pair geometry for P in PF3Cl2 ? What is the the shape (molecular geometry) of PF3Cl2?
Sp[tex]3[/tex] hybridization of a molecule with two lone pairs is present. This molecule's geometry is determined by its electron pair structure. If more than one bond angle is possible, separate each one with a space.
What is hybridization?The process of combining two atomic orbitals to produce a new variety of hybridized orbitals is described as hybridization. Usually, this mixing creates hybrid orbitals with entirely different energies, shapes, and other characteristics. Atomic orbitals with the same energy level are primarily responsible for hybridization. However, if the energies of the orbitals are equal, the process can involve both fully filled and partially filled orbitals. We can better understand bond formation, bond energies, and bond lengths by using the hybridization concept, which is an extension of valence bond theory. During the hybridization process, which primarily entails the merging of two orbitals, two "p" orbitals, or the mixing of a "s" orbital with a "p," the atomic orbitals of comparable energies are mixed together.To learn more about valence bond theory refer to:
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what is the formal charge on phosphorus in a lewis structure for the phosphate ion that satisfies the octet rule?
The formal charge on phosphorus in a lewis structure for the phosphate ion that satisfies the octet rule is 0.
What is a Lewis structure?
All valence electrons are represented by Lewis structures, which are structural formulas for molecules and polyatomic ions. These structural formulas are commonly referred to as Lewis dot structures since valence electrons are frequently shown as dots.
Why is Lewis structure used?
Chemical bonds and atomic structures are examined and understood using Lewis structures. The type of bonds created between atoms using valence electrons or/and lone pairs, as well as the number of bonds an atom can or will form with other atoms, can all be determined using Lewis dot diagrams.
Lewis structure of phosphate (po43-) ion.Formal charge= no. of valence electrons - no. of non bonding valence electrons- [tex]\frac{total no. of bonded electrons }{2}[/tex]
Formal charge of P= 5-0-[tex]\frac{10}{2}[/tex] = 0
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any area that has been treated with talcum powder or skin lotion must be rubbed with ________ to remove the residue and facilitate the adherence of the leads.
Any area that has been treated with talcum powder or skin lotion must be rubbed with alcohol to remove the residue and facilitate the adherence of the leads.
What is Alcohol?This is referred to as a substance which is derived from the fermentation of sugar under anaerobic conditions and it usually has an intoxicating effect.
However, it is also used for other purposes such as skin care and is usually applied after it has been treated with talcum powder or skin lotion so as to remove the residue and facilitate the adherence of the leads thereby making alcohol the correct choice in this scenario.
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this is the chemical formula for cassiterite (tin ore): a geochemist has determined by measurements that there are moles of tin in a sample of cassiterite. how many moles of oxygen are in the sample? round your answer to significant digits.
There are two moles of oxygen in cassiterite (tin ore), SnO2, for every mole of tin. As a result, if we have 13 moles of tin, we should have 13 * 2 moles of oxygen. This results in 26 moles of oxygen.
Cassiterite (SnO2) is the most essential tin ore, and it is frequently located in granite veins, granite pegmatites, and greisen. The name is derived from the Greek kassiteros, which means tin.
Cassiterite is a tin oxide mineral with the chemical formula SnO2. It is the primary significant source of tin, accounting for the majority of the world's supply. Primary cassiterite is found in trace amounts in igneous and metamorphic rocks all over the world. It is a mineral that can be found in soils and sediments. Cassiterite is more resistant to deterioration than many other minerals, so it is found in stream and shoreline sediments. Colors include black, brownish black, reddish brown, brown red, yellow, gray, and white.
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how to balance: CaCl2(aq) + Na3PO4(aq) ⟶ Ca3(PO4)2(s) + NaCl(aq)
can someone explain how to do it? thanks
The given double displacement reaction can be balanced as written below:
[tex]\rm 3CaCl_{2} + 2Na_{3}PO_{4} \rightarrow Ca_{3}PO_{4} + 6 NaCl \\[/tex]
What is displacement reaction?Displacement reactions are those in which one or two groups are replaced to form the new products. There are both single displacement reaction and double double displacement reactions.
In single displacement reactions, only one reactant will be replaced in the reaction whereas in double displacement reactions, two groups from the reactants are exchanged each other.
In the given reaction, the phosphate group is replaced to Ca and the Cl is group is shifted to Na metal as written in the chemical equation.
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How many liters (L) of water need to be added to prepare 1000mL of
0.3M NaCI from a 5M NaCI stock solution?
The amount, in liters, of water needed to be added to prepare 1000 mL of 0.3 M NaCl from a 5 M NaCl stock solution would be 0.94 L.
Dilution problemAccording to the dilution principle, the number of moles of solutes before dilution must be equal to the number of moles of solutes after dilution. This is mathematically expressed as:
[tex]m_1v_1[/tex] = [tex]m_2v_2[/tex]
Where [tex]m_1[/tex] and [tex]m_2[/tex] are molarities before and after dilution, and [tex]v_1[/tex] and [tex]v_2[/tex] are volumes before and after dilution.
In this case, [tex]m_1[/tex] = 5 M, [tex]m_2[/tex] = 0.3 M, [tex]v_2[/tex] = 1000 mL.
Let's find [tex]v_1[/tex]:
[tex]v_1[/tex] = [tex]m_2v_2[/tex] /[tex]m_1[/tex]
= 0.3x1000/5
= 60 mL
In other words, the volume of the stock solution to be taken is 60 mL. This volume has to be diluted by water to the 1000 mL mark. Thus, the amount of water to be added would be:
1000 - 60 = 940 mL
940 mL = 0.94 L
In summary, 0.94 L of water will be required to prepare the solution.
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F. According to the rules for naming compounds that you learned in this course, what is the
chemical name of this new product? What is its common name? (2 points)
Molecular compounds are termed by using the stem of the first element's name plus the suffix -ide, followed by the second element. Numerical prefixes are used to specify the number of atoms in a molecule.
What does "chemical common name" mean?The IUPAC defines a common name as one that clearly identifies a chemical but does not adhere to the current systematic naming convention. Acetone, which bears the scientific term, serves as an illustration of a common name. 2-propanone
What is the short answer to chemical?A chemical is any substance whose composition is known. A chemical always consists of the same "substance," to put it another way. Water is one of the substances found in nature.
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(d) Caesium is another element in Group 1 of the Periodic Table.
(i) The table below lists some statements about the reaction of caesium with
cold water compared to the reaction of lithium with cold water.
Place ticks (✓) in the boxes to show the two correct statements.
the reaction with caesium is more vigorous
the reaction with caesium produces a different gas
the reaction with caesium produces an acidic solution
the reaction with caesium produces a different compound
the reaction of caesium is endothermic
Answer: The reaction with caesium is more vigourus.
The reaction with caesium produces different compund.
Explanation:
Cold water and cesium react to produce hydrogen gas and a mixture of cesium and hydroxide ions as byproducts.
ip the electron in a hydrogen atom with an energy of -0.544 ev is in a subshell with 18 states. part a what is the principal quantum number, n, for this atom?
The principle quantum number(n) for this atom is 5
The position in an atom's shells and the size of an electron orbital are described by the primary quantum number, which is the most significant. The quantum number connected to the angular momentum of an atomic electron is called the azimuthal quantum number.
The energy of the electron in a hydrogen atom [tex]E_{n} = -0.544eV[/tex]
For hydrogen, Z = 1
The principal quantum number for [tex]n[/tex] for this atom is calculated by for this atom is determined using Bohr's atomic model,
So that [tex]E_{n} = \frac{-13.6(Z)^{2}}{n^{2}}eVatom^{-1}[/tex]
Where [tex]n[/tex] is the principal quantum number, [tex]E[/tex] is the energy, and [tex]Z[/tex] is the atomic number The values are substituted,
=> [tex]-0.544eV = -\frac{13.6(1)^{2}}{n^{2}} eVatom^{-1}[/tex]
[tex]n^{2} = -\frac{13.6}{-0.544} \\n^{2} = 25\\n = 5[/tex]
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the epicardial fat pad . a. can be mistaken for a pericardial effusion b. appears heteroechoic and moves with the heart c. is always visible in all cardiac views d. all of the above e. a and b onl
The epicardial fat pad . a. can be mistaken for a pericardial effusion b. appears heteroechoic and moves with the heart.
It is the posterior fat pad that is a sign that indicates a pathology when one looks at an x-ray. When a crescent fat is observed in the x-ray, it indicates there is an elbow joint effusion since normally the posterior fat cannot be seen from the x-ray.
In radiography, X-rays are used to view inner parts of the body for medical observation, analysis and to know the treatment procedure to adopt.
When a non visible posterior fat pad on a well-exposed, then it generally suggests a negative study for injury. This means that the features observed are unrelated to any type of injury. This eliminates option c.
Therefore, only option a and b are correct that the epicardial fat pad . a. can be mistaken for a pericardial effusion b. appears heteroechoic and moves with the heart.
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explain the difference in behavior between water and the buffer with addition of acid or base. are your results as expected? why or why?
The adding of an acid or base to a buffer seems to have no effect on the pH of the buffer. In contrast, going to add acid or base to unbuffered water drastically changes the pH.
Any hydrogen-containing substance skilled of making a donation a proton (hydrogen ion) to that other substance is defined as an acid. A base is a compound or ion that really can accept an acid's hydrogen ion. The sour flavours of weak acids is generally described by the contaminant that emits hydrogen ions in water and formation salts by incorporating with these metals. Acids have a bitter aftertaste and cause certain dyes to turn red. buffer is an aqueous solution that withstands adjustments in pH upon on the addition of either an acid or a base". Furthermore, adding water to a buffer or going to allow it to evaporate from of the buffer has no significant effect just on pH of the buffer.
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a brittle white crystalline solid has a melting point of 760 c and reacts when added to water. this substance is most likely what type of solid
A brittle white crystalline solid reacts with when added to water is Quartz. It is a metamorphic solid.
Quartz is the most abundant silica mineral. Pure Quartz is colorless and transparent. It occurs in most igneous and practically all metamorphic and sedimentary rocks. It is used as a component of numerous industrial materials. Silicon (Si) has the atomic number 14 and is closely related to carbon. It is a relatively inert metalloid. Silicon is often used for microchips, glass, cement, and pottery. Silica is the most abundant mineral found in the crust of the earth. One of the most common uses of silica quarts is the manufacturer of glass. Quartz is the second most abundant mineral in the Earth's crust. Its chemical name is SiO2.
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calculate the standard gibbs free energy associated with the formation of ammonia from nitrogen and hydrogen at 25 c and 500 c
-23.4kj is the standard gibbs free energy associated with the formation of ammonia from nitrogen and hydrogen at 25 c and 500 c
-
The temperature is 25 deg C or 298 K.
ΔGo =−RTlnK=−8.314×298×ln1.3×104 =−23469J=−23.4kJ
Hence, the standard free energy change is -23.4 kJ
Gibbs free energy, thermodynamics The word "free energy" refers to a thermal potential that can be utilized to determine the maximal amount of work that a thermodynamically closed system can perform at constant pressure and temperature. The change in limitless energy that occurs when a chemical is created from its components in their most thermodynamically states under appropriate conditions is referred to as the free basic energy of formation. Ammonia is a colourless gas that has a strong suffocating odour. It easily dissolves in the water, forming an ammonium hypochlorite that can cause discomfort and burns. Under pressure, ammonia gas compresses easily and formation a clear, colourless liquid.
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Draw the Lewis structure for SF6 and then answer the following questions that follow.
-Do not include overall ion charges or formal charges in your drawing.
Questions:
1). What is the electron-pair geometry for S in SF6?
2). What is the shape (molecular geometry) of SF6?
SF6 molecular geometry will be octahedral because if we look at the structure sulphur hexafluoride has a central sulphur atom around which12 electrons or 6 electron pairs are present and there are no lone pairs.
What is SF6?Sulphur hexafluoride – also known as SF6 – is a ‘greenhouse gas’ that has long played a part in global warming, similar to that of carbon dioxide (CO2).CO2 has been a focal point of climate change for many years. Released from the burning of fossil fuels and other carbon-intensive practices, it creates a cover that traps heat from the sun in the earth’s atmosphere, warming the planet and the oceans. This is what’s known as the ‘greenhouse effect’.SF6 also has this effect, but is much more potent than CO2. Today, wider understanding of the potency of this gas – and the need to reach net zero carbon emissions by 2050 in order to tackle climate change – is causing a rethink of its use.To learn more about ‘greenhouse effect’ refer to:
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Which of the following concentration measures will change in value as the temperature of a solution changes?
1. mass percent
2.mole fraction
3. molality
4. molarity
5. all of these
The concentration measures will change in value as the temperature of a solution changes is molarity. The correct option is 4.
What is molarity?The molarity of a substance refers to how much of it is present in a given volume of solution (M). Molarity is the measure of how many moles of a solute are present per liter of a solution. Molarity is also referred to as a solution's molar concentration.
To find the equation for molarity, divide the volume of solvent used to dissolve the given solute by the number of moles of that solute. M = n V
Since the volume of the solution rises as the temperature rises, molarity decreases. Therefore, molarity is normally affected when therefore is a change in temperature of a solution either when it increases or decreases.
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methylhydrazine (ch6n2) is commonly used as a liquid rocket fuel. when 4.00 g of methylhydrazine is combusted in a bomb calorimeter, the temperature of the calorimeter increases from 25.00 oc to 39.05 oc. in a separate experiment the heat capacity of the calorimeter is measured to be 7.794 kj/oc. what is the heat of reaction for the combustion of a mole of ch6n2 in this calorimeter?
The heat of reaction for the combustion of a mole of C₆NH₂ in this calorimeter is - 1.30 × 10³ kJ/mol.
The reaction is given as :
2CH6N2(l) + 5O2(g) ----> 2N2(g) + 2CO2(g) + 6H2O(l)
given that :
initial temperature = 25 °C
final temperature = 39.05 °C
heat capacity of the calorimeter = 7.794 kJ/°C
mass of methylhydrazine = 4 g
molar mass of methylhydrazine = 46.1 g/mol
the heat of reaction Q = - C ΔT
= - 7.794 × ( 39.05 - 25)
= - 113.0 kJ
the heat of reaction of a mole = - (113.0 kJ / 4) × 46.1
= - 1.30 × 10³ kJ/mol
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what are the correct coefficients if the law of conservation of mass is applied to the decomposition of solid ammonium nitrite to nitrogen gas and liquid water?
Ammonium nitrite, NH4NO2, will decompose to yield nitrogen gas and water Vapor by the following equation:
NH4NO2(s)--->2H2O(g)+N2(g)
A decomposition reaction can be defined as a chemical reaction in which one reactant breaks down into two or more products. As per law of conservation of mass, the mass of your initial substances (reactants) will be the same as the mass of the substances that you get after the reaction has occurred (products). The mass will stay the same because the number of each kind of atom stays the same. The mass will increase because a new kind of molecule is formed. The principle is that the mass of matter, in a closed system, will always be the same no matter what type of change happens to the matter. Whether it's a change in state, or dissolving, or a chemical reaction, or any combination of these, the amount of mass will not change.
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You are approached by a neighboring group of human survivors and they are wanting to know what you are shooting at the alien craft so you can see them at night. Choose the right explanation for this effect.
a Chemicals in the paint absorb light energy in a process called phosphorescence, radioactive elements keep the glow going.
b Key element is sulfur and the sulfur creates light after being heated in a process called sulfunescense
c Chlorine is the reason why the alien vessels glow.
d Calcium make the light when the craft comes into contact with water
Atoms of different element can not have same atomic number because only same type of atoms combine to form element. Atoms belonging to different element can have different atomic number. Therefore, the correct option is option A.
What is element?Element generally consist of atoms or we can atoms combine to form element. Atoms of an element is always same, means all the properties of all atoms of one type of element is same.
Two or more than two atoms with different physical or chemical properties can not combine together to form an element. Chemicals in the paint absorb light energy in a process called phosphorescence, radioactive elements keep the glow going.
Therefore, the correct option is option A.
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Please help with this:
Typically, hard water used in a lab class would have been prepared by adding 1 gram of
magnesium sulfate per liter of distilled water. Magnesium sulfate contains 20.2%
magnesium ions by mass. What is its hardness in grains per gallon (GPG)? (One GPG
equals 17.1 mg/L.)
One grain of calcium carbonate, or 64.8 milligrams, is dissolved in one US gallon of water to represent one grain per gallon (gpg), a measure of water hardness (3.785412 L).
What is Water Hardness Measurement Scales?Understanding your test findings necessitates familiarity with the many water hardness testing scales that are employed. The majority of results are provided as a number that indicates the amount of calcium carbonate or calcium carbonate equivalents present in a specific unit of water. Depending on the measurement method, this value may be given in grains per gallon (gpg), parts per million (ppm), or milligrammes per litre (mg/L).Per Gallon of Grains Measurement of water hardnessThe hardness scale, expressed in gpg of calcium carbonate, can be seen as follows, according to the Water Quality Association:Soft is defined as gpg less than 1.An intermediate level of difficulty is between 1 and 3.5 gpg.The category of fairly challenging ranges from 3.5 to 7 gpg.The hard range is between 7 and 10.5 gpg.It's regarded quite difficult to get above 10.5 gpg.To Learn more About grain per gallon refer to:
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(50 points)
Diurnal temperature range is the difference between ________ and ________ temperature each _________.
high, low, hour
high, low, day
beginning, ending, hour
beginning, ending, day
Answer: Diurnal temperature range is the difference between __maximum______ and ____minimum____ temperature each ___1 day______.
Explanation:
the solubility of caf2 is measured to be 0.017 g/l. based on this information, what is ksp for caf2? the molar mass of caf2 is 78.075 g/mol.
The molar mass of caf2 is 78.075 g/mol is 4.14 x 10^ -11.
CaF2 (s) <----> Ca2+ (aq) + 2F- (aq)
At equilibrium [Ca2+] = S , [F-] = 2S , where S is amount of CaF2 dissolved i.e solubility.
The molar mass of a chemical compound is determined by dividing its mass by the quantity of that compound, expressed as the number of moles in the sample, measured in moles. The molar mass of a material is a bulk attribute rather than a molecular one.
given S = 1.7 x 10^ -2 g/L = 0.017 g/L
we can convert g/L to mol/L by dividing S with Molar mass of CaF2
S in mol / L = (S in g/L) / ( CaF2 molar mass) = ( 0.017g/L) / ( 78.07g/mol) = 0.000218 mol /L
[F-] = 2S = 2 x ( 0.000218) = 0.000436 mol/L
now Ksp = [Ca2+] [F-]^2
= ( 0.000218 ) (0.000436 )^2
= 4.14 x 10^ -11
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ammonium ion (nh4 ) is an acid that can dissociate to form ammonia (nh3) and h in aqueous solution. the pka for this reaction is 9.25. when total ammonium ion is 50% dissociated, what is the ph?
When total ammonium ion is 50% dissociated, The pH is 9.25.
Given, the pKₐ of ammonium ion (NH₄⁺) is 9.25.
The dissociation of NH₄⁺ to ammonia (NH₃) and H⁺ in aqueous solution is represented below.
It is stated that the ammonium ion is 50% dissociated in the solution. Therefore the concentration of each species at that instant [if started with 1M conc. of NH4+ (aq)] is summarized as follows:
NH4+ (aq) ⇌ NH3 (aq) + H+ (aq)
Initial conc. (in M) 1 - -
At 50% dissociation 1-0.5, i.e., 0.5 0.5 0.5
The given value of pKₐ immediately reminds us of the form of Henderson-Hasselbalch equation containing pKₐ , i.e.,
pH = pKₐ + log₁₀ [tex]\frac{[salt]}{[acid]}[/tex] _ _ _(i)
But, NH₄⁺ (aq) exists as the conjugate acid form, as well as the salt (ionized) form. Hence, we cannot use equation. (i) for our calculations.
Therefore, we need to convert the above value of Kₐ to the equivalent Kb (for NH₃), corresponding to the reverse equilibrium.
This is achieved by using the relation
Kb = [tex]\frac{Kw}{Ka}[/tex]
or, -log₁₀ Kb = -log₁₀ Kw + log₁₀ Ka
or, pKb = pKw - pKa = 14 - 9.25 = 4.75
where, pKw = 1 x 10⁻¹⁴ (at 298 K).
Therefore, pKb of ammonia (NH₃) = 4.75
Now, we need to use the form of Henderson-Hasselbalch equation which uses Kb; which is in fact
pOH = pKb + log₁₀ [tex]\frac{[salt]}{[base]}[/tex] _ _ _(ii)
where the salt is NH₄⁺, and the base is NH₃. Further, we know that
Kw = [H⁺][OH⁻] or, pOH + pH = pKw = 14 or, pOH = 14 - pH
Substituting this relation in eq. (ii) gives
14 - pH = pKb + log₁₀ [tex]\frac{[NH4+]}{[NH3]}[/tex]
or, pH = 14 - pKb — log₁₀ [tex]\frac{[NH4+]}{[NH3]}[/tex]
As calculated, pKb = 4.75, [NH₄⁺] = 0.50 M, while [NH₃] = 0.50 M, assuming we start with a conc. of 1M NH₄⁺. Hence,
pH = 14 – 4.75 – log₁₀ [tex]\frac{0.50}{0.50}[/tex]
= 9.25 - log₁₀ ( 1 )
= 9.25 - 0
pH = 9.25
Hence, the pH of a solution consisting of 50% NH₃ and 50% NH₄⁺ will be equal to 9.25.
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select true or false: more energy is required to break a bond with an order of 3/2 than is required to break a bond of order 2.
Answer: The answer is false
Explanation: