What combination of substances will give a buffered solution that has a pH of 5.05? (Assume each pair of substances is dissolved in 5.0 L of water.) (Kb for NH3 = 1.8 ´ 10–5; Kb for C5H5N = 1.7 ´ 10–9) Select one: a. 1.0 mole NH3 and 1.5 mole NH4Cl b. 1.5 mole NH3 and 1.0 mole NH4Cl c. 1.0 mole C5H5N and 1.5 mole C5H5NHCl d. 1.5 mole C5H5N and 1.0 mole C5H5NHCl e. none of these
Answer:
c. 1.0 mole C5H5N and 1.5 mole C5H5NHCl
Explanation:
We can determine pH of a buffer using H-H equation:
pH = pKa + log [A⁻] / [HA]
Where [A⁻] is concentration of conjugate base and [HA] concentration of weak acid. These concentrations can be computed as moles of each species.
We need to determine pKa of both NH₃ and C₅H₅N buffers, thus:
pKb = -log Kb
NH₃ pKb = -log 1.8x10⁻⁵ = 4.74
C₅H₅N pKb = -log 1.7x10⁻⁹ = 8.77
And pKa = 14 - pKb:
NH₃ pKa = 14 - 4.74 = 9.26
C₅H₅N pKb = 14 - 8.77 = 5.23
A buffer works only under pH's between pKa-1 and pKa + 1. As pKa NH₃ buffer is 9.23 is not possible to produce a buffer with pH 5.05 for this system.
Thus, we only will compute the buffers made with C₅H₅N:
c. 1.0 mole C5H5N (Weak base) and 1.5 mole C5H5NHCl (Conjugate acid)
pH = pKa + log [A⁻] / [HA]
pH = 5.23+ log [1.0 moles] / 1.5 moles]
pH = 5.05d. 1.5 mole C5H5N and 1.0 mole C5H5NHCl
pH = pKa + log [A⁻] / [HA]
pH = 5.23+ log [1.5 moles] / 1.0 moles]
pH = 5.41Right solution is:
c. 1.0 mole C5H5N and 1.5 mole C5H5NHCl3. Prepare a saturated solution of common salt in hot water. Suspend a thick cotton wick into this solution. Keep it undisturbed for a few days. You will find that common salt crystals will deposit on the wick. Is the change physical or chemical?
Answer:
physical
Explanation:
The change is physical.
A physical change involves a reversible change to the physical properties of substances, whereas a chemical change involves an irreversible change to the chemical properties of substances through a chemical reaction.
The dissolution of common salt is a physical change because the common salt can be retrieved by evaporating off the water. This is what was manifested by the deposition of common salt crystals on the wick.
5. What distinguishes the noble gases from other elements in the main group?
How does this contribute to the tendency for the various elements to react
with each other?
Answer:
Noble gases are the least reactive of all known elements. Their outer energy levels are full because they each have eight valence electrons. ... As a result, noble gases cannot become more stable by reacting with other elements and gaining or losing valence electrons.
Explanation:
Noble gases have complete valence shells so they do not participate in the reactions while the other elements in the main group have incomplete valence shells so they participate in the reaction to complete it.
What are noble gases?Noble gases can be described as the six elements that belong to the 18th group of the modern periodic table. The elements of group 18 are Helium, Neon, Argon, Krypton, Xenon, and Radon.
Under normal temperature and pressure conditions, all noble gases exist in the gaseous state and exhibit low chemical reactivity hence they are also referred to as inert gas. All noble gases possess stable electronic configurations because their valence shell is fully filled.
Noble gases are generally found as mono-atomic gases. The general electronic configuration group 18 elements can be written as ‘ns²np⁶’ where n is the principal quantum number.
Therefore, the reactivity of the noble gases can be distinguished from other elements in the main group.
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Which is one way scientist communicate the results of an experiment?
Answer:
By writing an experiment report
Explanation:
Sodium hydroxide and water will react at room temperature. What does this indicate about its activation energy? A. The activation energy is very low. B. The activation energy is at exactly 600 kJ. C. The activation energy is very high. D. The reaction cannot reach activation energy.
Answer:
The answer would be C.
Explanation:
I took a test with the same question.
The activation energy is very high. Hence, option C is correct.
What is activation energy?Activation energy is the sufficient amount of energy necessary to initiate a chemical reaction.
When sodium hydroxide (NaOH) dissolves in water, it is distributed into positively-charged sodium ions and negatively - charged hydroxide ions.
These cations and anions move around in the water, free and independent of each other, though cations tend to be surrounded more closely by anions and vice versa.
Hence, when sodium hydroxide and water will react at room temperature, the activation energy is very high.
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how many significant figures are in 820 400.0 L
Answer:
7 significant numbers
PLS HELP ASAP 15 POINTS TYSM which of the following is a consequence of urban heat islands? a) increased precipitation downwind of the city b) increased winds within the city c) increased precipitation upwind of the city d) decreased winds within the city
Answer:
Hey!
Your answer is definitely A!
Explanation:
Hope this helps!
:>
In an ecosystem, the following is a consequence of urban heat islands which is increased precipitation downwind of the city.
What is an ecosystem?Ecosystem is defined as a system which consists of all living organisms and the physical components with which the living beings interact. The abiotic and biotic components are linked to each other through nutrient cycles and flow of energy.
Energy enters the system through the process of photosynthesis .Animals play an important role in transfer of energy as they feed on each other.As a result of this transfer of matter and energy takes place through the system .Living organisms also influence the quantity of biomass present.By decomposition of dead plants and animals by microbes nutrients are released back in to the soil.
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Which Nobel gas electron structures do the atoms in a
molecule of hydrogen chloride attain?
And can you tell me why aswell please?
Answer:
The noble as structures attained are helium and argon
Explanation:
The electron configuration of chlorine atom is 1s²2s²2p⁶3s²3p⁵
The elecron configuation of hydrogen is 1s¹
The electron configuration of argon atom is 1s²2s²2p⁶3s²3p⁶
The elecron configuation of helium gas is 1s²
Therefore, in the hydrogen chloride molecule the hydrogen and the chlorine each share one electron from the other atom to attain the the stable noble gas structure of helium for hydrogen and argon for chlorine.
In 1838 botanist Matthias Schleiden determined that all plants are composed of cells. In 1839, anatomist Theodor Schwann proposed that all animals are composed of cells. In 1855, biologist Rudolph Virchow added to Schleiden's and Schwann's observations and proposed that all living things are composed of cells. Which statement is also part of Virchow's cell theory?
Answer:
cells arose from preexisting cells
Explanation:
Rudolph Virchow is a German biologist that built on the work of other scientists such as Theodor Schwan to contribute his own quota to the development of the cell theory as it is currently known.
After several studies, Virchow rejected the idea of spontaneous generation and accepted the initially rejected idea of cell division. He earlier believed that cell division only takes place is some special type of cells and not in all cells.
Even though Virchow was not the first to bring the idea of cells arising from preexisting cells, he was the one that popularized the idea and added it to the earlier belief that all living organisms are made up of cells.
Answer:
B
Explanation:
According to Dalton, the pressure of a mix of gases in a single container is the sum of all of the pressures of the individual gases: Ptotal = Pa + Pb + … If a 20.0L container at 30°C has 3.4 atm of methane and 1.68 atm of ethane, what is the total pressure of the container?
Answer:
The correct answer is 5.08 atm
Explanation:
This question tests our knowledge of the Dalton's law of partial pressures which is stated in the question; that the pressure of a mixture of non-reacting gases in a single container is the sum of all the pressures of the individual gases.
It can hence be represented mathematically as Ptotal = Pa + Pb + ...
Ptotal = pressure of methane + pressure of ethane
Ptotal = 3.4 atm + 1.68 atm
Ptotal = 5.08 atm
What is the lowest value of n that allows g orbital to exit
which of the following compounds is carbon tetrafluoride
Answer: CF4 is the formula
Explanation:
Answer:
CH4
Explanation:
This answer is for APEX
3. How did ethanol use affect the shortage of corn available to consumers during and
after the drought of 2012? Do you think that commodities in one sector should be used
in another economic sector? How might the concept of needs and wants affect your
analysis of this issue?
Due to drought, the production of corn decreases and shortage of it occurs.
Effects of droughtYes, commodities in one sector should be used in another sector because scientist invented methods in which one commodity is used in several sectors for the production of new products.
Corn was used for the production of ethanol which causes the shortage of corn that was available to consumers during and after the drought condition of 2012 so we can conclude that due to drought, the production of corn decreases and shortage of it occurs.
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(30 points) alright so there’s this girl I’m ab to slide in her dms I just need a pickup line but nothing inappropriate bc I don’t like to slide in thirsty so if anyone has a completely hydrated cute pickup line help a simp out
Answer:
Are you a fruit, because honeydew you know how beautiful you look right now?
or maybe
I hear you’re good at algebra…..Will you replace my eX without asking Y?
or maybe
On a scale of one to ten you’re a nine… Because I’m the one left that you need.
Explanation:
Hope these help you.
A two digit number is such that the sum of the ones and the tens digits is tens.If the digits are reversed,the new number formed exceeds the originals numbers by 54.Find the number.
Answer:
Explanation:
Let the no in the ones place be x
And the no in the tens place be 10 - x
Original no = 10 ( 10 - x ) + x
= 100 - 10x + x
= 100 - 9x
Reversed no = 10 - x + 10 ( x )
= 10 - x + 10 x
10 + 9x
According to the question,
the new number formed exceeds the originals numbers by 54.
10 + 9x = 100 - 9x + 54
10 + 9x = 154 - 9x
By transposing,
9x + 9x = 154 - 10
18 x = 144
x = 144 / 18
x = 8
∴ Digit in ones place = x = 8
Digit in tens place = 10 - x = 10 - 8 = 2
So the number = 28
( You can also recheck it by adding the ones and tens digit
8 + 2 = 10
In the question, the sum of ones and tens digit in ten )
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please help :) How can scientists ensure that their data are reliable? A) by making a single observation B) by recording values without units C) by keeping the results private D) by repeating trials during an experiment
Answer:
D. by repeating trials during an experiment
Explanation:
chile its actually d
Explanation:
Polymers formed from amino acids are called _____. proteins carbohydrates lipids nucleic acids
Answer:
Proteins
Explanation:
Amino acids act as monomers (a single unit used to form polymers) , the polymer will be a long chain of individual amino acids. An amino acid chain forms a protein. These proteins are also known as peptides.
Hope this helps and please mark as the brainliest.
In a mass spectrometer, the ions are sorted out in which of the following ways?
A. By accelerating them through electric field
B. By accelerating them through magnetic field
C. By accelerating them through electric and magnetic field
D. By applying a high voltage
Answer:
C
Explanation:
The ions are first accelerated electrically, and then bended magnetically to sort them and record them.
How many gram of zinc will have to be treated with dilute hydrochloric acid to liberate 1.85 dm³ of hydrogen at 27°C and 750mmHg?
Answer:
Explanation:
given
volume=1.85 d m^3
T=27 degree C=27+273 k=300 k
P=750 mmHg
mass of zinc=?
we know that PV=nRT
n=m/M
PV=mRT/M
M for zinc=65.4
PVM=mRT
m=PVM/RT
m=750*1.85*65.4/0.0821*300
m=90742.5/24.63
m=3684
hope this will help u
The electron in a hydrogen atom can undergo a transition from n = 4 to n = 3, emitting a photon with energy 1.06 × 10 –19J. Use this transition to answer the following questions.
i. What is the wavelength of this transition?
ii. How does this transition show that the position of the electron is quantized?
Answer:
Wavelength (λ) = 1.875 × 10⁻⁶ m
Explanation:
Given:
Energy (e) = 1.06 × 10⁻¹⁹ J
Find:
Wavelength (λ) = ?
Computation:
e = hc / λ
λ = hc / e
where c = 3 × 10⁸
Planck's constant (h) = 6.625 × 10⁻³⁴
So,
Wavelength (λ) = (6.625 × 10⁻³⁴)(3 × 10⁸) / (1.06 × 10⁻¹⁹)
1. Wavelength (λ) = 1.875 × 10⁻⁶ m
2. Given n = 4 to n = 3 both are integer not fraction so, electron is quantize
in the symbol 3p4
a. the 3 represents the principal energy level
b. the p represents the principal energy level
c. the 4 represents the principal energy level
d. all of the above
help!
Answer:
a. the 3 represents the principal energy level
Explanation:
3 is the principal energy level. The p is the sublevel. 4 is the possible occupying electron.
What is the molarity of a 50.0ml aqueous solution containing 10.0 grams of hydrogen peroxide H2O2
Molarity= No of moles of solute * 1000 / vol solution in ml
No of moles= Given mass / Molar mass
Given Mass of solute (H2O2)= 10g
Molar mass of H2O2=34gmol^-1
No of moles= 10/34= 0.294 moles
Volume of solution=50ml
Molarity = 0.294*1000 / 50
Molarity = 5.8M
Easyyy plz
What Is the Reactivity Series? ...
Answer:
In chemistry the reactivity series is an empirical, calculated, and structurally analytical progression of a series of metals, arranged by their "reactivity" from highest to the lowest.
Answer:
In a reactivity series, the most reactive element is placed at the top and the least reactive element at the bottom. More reactive metals have a greater tendency to lose electrons and form positive ions.
A reactivity series of metals could include any elements. For example,
A list of elements from most reactive to least reactive: potassium, sodium, lithium, calcium, magnesium, aluminum, zinc, iron, copper, silver, and gold.
A good way to remember the order of a reactivity series of metals is to use the first letter of each one to make up a silly sentence. For example, People Say Little Children Make A Zebra Ill Constantly Sniffing Giraffes.
Observations of the way that these elements react with water, acids, and steam enable us to put them into this series.
The tables show how the elements react with water and dilute acids:
Element Reaction with water
Potassium Violently
Sodium Very quickly
Lithium Quickly
Calcium More slowly
Element Reaction with dilute acids
Calcium Very quickly
Magnesium Quickly
Zinc More slowly
Iron More slowly than zinc
Copper Very slowly
Silver Barely reacts
Gold Does not react
Note that aluminum can be difficult to place in the correct position in the reactivity series during these experiments. This is because its protective aluminum oxide layer makes it appear to be less reactive than it really is. When this layer is removed, the observations are more reliable.
Non-metals in the reactivity series
It is useful to place carbon and hydrogen into the reactivity series because these elements can be used to extract metals.
Here is the reactivity series including carbon and hydrogen:
A list of elements from most reactive to least reactive: potassium, sodium, lithium, calcium, magnesium, aluminum, carbon, zinc, iron, hydrogen, copper, silver, and gold.
Note that zinc and iron can be displaced from their oxides using carbon but not using hydrogen. However, copper can be extracted using carbon or hydrogen. Displacement reactions of metal oxides
A more reactive metal will displace a less reactive metal from a compound. The thermite reaction is a good example of this. It is used to produce white-hot molten (liquid) iron in remote locations for welding. A lot of heat is needed to start the reaction, but then it releases an incredible amount of heat, enough to melt the iron.
aluminium + iron(III) oxide → iron + aluminium oxide
2Al + Fe2O3 → 2Fe + Al2O3
Because aluminum is more reactive than iron, it displaces iron from iron(III) oxide. The aluminum removes oxygen from the iron(III) oxide:
iron is reduced
aluminum is oxidized
Reactions between metals and metal oxides allow us to put a selection of metals into a reactivity series. Using metals A, B, and C:
Metal A Metal B Metal C
A oxide X Displaces A Displaces A
B oxide No reaction X No reaction
C oxide No reaction Displaces C X
Metal A cannot displace either B or C - so it must be the least reactive and be at the bottom of this reactivity series.
Metal B displaces both A and C - so it must be the most reactive and be at the top of this reactivity series.
Metal C displaces A but cannot displace B - so it must be more reactive than A but less reactive than B, and be in between them in this reactivity series.
In general, the greater the difference in reactivity between two metals in a displacement reaction, the greater the amount of energy released.
Aluminum is much higher than iron in the reactivity series, so the thermite reaction releases a lot of energy. Magnesium is very high in the reactivity series, and copper is very low - so the reaction between magnesium and copper oxide is more violent.
Therefore, the order is:
A list of letters from most reactive to least reactive: B, C and A,
Displacement reactions of solutions
A more reactive metal will displace a less reactive metal from a solution of one of its salts. For example:
magnesium + copper(II) sulfate → copper + magnesium sulfate
Mg(s) + CuSO4(aq) → Cu(s) + MgSO4(aq)
In this reaction, the blue color of the copper(II) sulfate fades as it is used up (magnesium sulfate solution is colorless). We would also see copper metal forming.
Reactions between metals and solutions of metal salts allow us to put a selection of metals into a reactivity series. Using metals J, K, and L:
Metal J Metal K Metal L
J sulfate X No reaction No reaction
K sulfate Displaces K X Displaces K
L sulfate Displaces L No reaction X
Metal J displaces both K and L - so it must be the most reactive and be at the top of this reactivity series.
Metal K cannot displace either J or L - so it must be the least reactive and be at the bottom of this reactivity series.
Metal L displaces K but cannot displace J - so it must be more reactive than K but less reactive than J, and be in between them in this reactivity series.
- sorry I'm late and it's is long -_-||
how many oxygen atoms are in 7.25g of calcium nitrate
Answer:
The answer to this question is approximately equal to 1.6 ×
[tex] 1.6 \times {10}^{23} atom \: o[/tex]
In science class, Jake mixed water with differing amounts of an unknown liquid. After mixing the liquids, he heated 20 milliliters (ml) of each mixture and observed how quickly it boiled. The table shows his results.
According to the question, each mixture decrease the boiling point of the water.
What is boiling point ?Boiling temperature is defined as the temperature at which liquid change into a vapour at the atmospheric pressure at sea or ocean level.
For example the boiling temperature of water is 100 degree celcius.
Thus, each mixture decrease the boiling point of the water, option "A" is correct.
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absorption of digested food takes place in the
Answer:
Explanation:
Absorption of digested food takes place in the small intestine.
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Answer:
Absorption of digested food takes place in the small intestine.
Explanation:
Atoms contain positive and negative charges. Why is the overall charge on an atom neutral?
A. Atoms contain the same amount of protons and electrons, and their charges cancel out.
B. The nucleus of an atom contains neutrons, which keep the positive and negative charges balanced.
C. Atoms are all negatively charged because electrons are on the outside of the atom.
D. Atoms contain the same amount protons and neutrons, and their charges cancel out.
Answer:
Atoms contain the same amount protons and neutrons, and their charges cancel out.
Explanation:
Answer via Educere/ Founder's Education
Atoms contain positive and negative charges, the overall charge on an atom neutral because Atoms contain the same amount of protons and electrons, and their charges cancel out.Hence, Option (A) is correct
What is an Atom ?
An atom is the smallest unit of ordinary matter that forms a chemical element.
Every solid, liquid, gas, and plasma is composed of neutral or ionized atoms.
Atoms are extremely small, typically around 100 picometers across.
An atom consists of a positively charged nucleus, surrounded by one or more negatively charged particles called electrons.
The positive charges equal the negative charges, so the atom has no overall charge; it is electrically neutral.Hence, Option (A) is correct
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You work in the special effects department of a movie studio. You are
currently working on a superhero movie where the hero is very strong
and can punch through metal. For the next scene you need to replace a
6 inch by 6 inch square of a metal wall with a different material that will
crumble when the actor hits it. What could you use?
A. You could use Carbon(C)
B. You could use Potassium (k)
C. You could use Titanium (T)
D. You could use Manganese (Mn)
Answer:
The correct option is;
D. Manganese (Mn)
Explanation:
Manganese is very brittle, hard, iron like silvery-gray metal, that is difficult to melt. In air, Manganese slowly disintegrate in a similar manner to iron rusting in water
Manganese and iron have similar chemical and physical properties however manganese is more harder and more brittle than iron
A brittle material is one that easily breaks without deforming elastically
Therefore, manganese, due to its very iron like appearance and brittle nature will be suitable to replace the metal wall and crumble easily when the actor hits it.
For the set of ionic compounds, LiCl, AgCl, PbCl2, choose the correct characterization of their solubilities in water from the response list. Group of answer choices All three salts are soluble. None of the three salts are soluble. Two of the three salts are soluble. One of the three salts is soluble.
Answer:
Two of the three salts are soluble.
One of the three salts is soluble.
Explanation:
One or two of the three salts would be soluble in water depending on if the water is cold or hot.
According to the solubility rules of chloride salts, all chlorides are soluble in cold water except for those of silver (Ag), lead (Pb), and mercury (I) (Hg).
This thus means that both AgCl and [tex]PbCl_2[/tex] would be insoluble in cold water while LiCl would be soluble.
[tex]PbCl_2[/tex] is, however soluble in hot water.
Hence, in cold water, one of the three salts (LiCl) would be soluble, while in hot water, two of the three salts (LiCl and [tex]PbCl_2[/tex]) would be soluble.
What are cells and how are they important to maintaining life?
Answer:
Cells are the "building blocks for all living things." Without cells, we couldn't survive. Cells do many important things. Some of the things they can do are taking in food nutrients, frame our bodies, and change the food nutrients into energy.
