Scientists improved Mendeleev’s early periodic table by ___.
including physical properties of elements such as melting point and density
including chemical properties of elements such as the ability to burn or to tarnish
using atomic number instead of atomic mass to organize the elements
using numbers of neutrons and protons to organize the elements by their properties

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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992 millimoles of zinc nitrate the chemist has added to the reaction flask.

Zinc nitrate is an inorganic compound with the formula Zn(NO₃)₂. This colorless, crystalline salt is extremely hydrophilic. it's generally encountered as a hexahydrate Zn(NO₃)₂·6H₂O. it's soluble in each water and alcohol. Zn Nitrate may be a colorless or white, odorless, crystalline (sand- like) solid or flake. it's used as a catalyst and a mordant for dyes, and in liquid plant food.

Chemists and materials scientists study substances at the atomic and molecular levels and analyze the ways that within which the substances move with each other. They use their information to develop new and improved product and to check the standard of factory-made product.

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A chemist adds 435.0mL of a 2.28 M zinc nitrate ZnNO32 solution to a reaction flask. Calculate the millimoles of zinc nitrate the chemist has added to the flask. Round your answer to 3 significant digits.

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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.

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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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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Answer: The hybridization that is involved in SF4 is sp3d type. Here will learn and understand how to determine SF4 hybridization. We will discuss the steps in detail.

Name of the Molecule Sulphur Tetrafluoride

Molecular Formula = SF4

Hybridization Type = sp3d

Bond Angle = 102o and 173o

Geometry = see-saw

Explanation:

In order to determine the hybridization of sulphur tetrafluoride, you have to first understand its Lewis structure and the number of valence electrons that are present. The SF4 molecule consists of a total of 34 valence electrons. Here 6 will come from sulphur and each of the four fluorine atoms will have 7 electrons.

During the formation of SF4, the sulphur atom will form bonds with each of the fluorine atoms where 8 valence electrons are used. Meanwhile, the four fluorine atoms will have 3 lone pairs of electrons in their octet which will further utilize 24 valence electrons. In addition, two electrons will be kept as lone pairs in the sulphur atom. Now we can determine sulphur’s hybridization by taking a count of the number of regions of electron density.

When bonding takes place there is a formation of 4 single bonds in sulphur and it has 1 lone pair. Looking at this, we can say that the number of regions of electron density is 5.

EXTERNAL LINKS :

https://www.chemtube3d.com/vseprshapesf4/

https://geometryofmolecules.com/sf4-lewis-structure-polarity/

The electrons in an atom are depicted in orbital diagrams in visual form. For creating orbital diagrams, three rules are helpful.

Each electron resides in the orbital with the , in accordance with the Auf Bau Principle.

According to the Pauli Exclusion Principle, an orbital can hold no more than two electrons. According to Hund's rule, electrons enter various orbitals within a single sub-level before doubling up within orbitals.

We have seen how the quantity and kind of valence electrons play a crucial role in establishing the chemical characteristics of a specific element. Due to their propensity to lose their single valence, Group 1A metals are extremely reactive.

Therefore, The electrons in an atom are depicted in orbital diagrams in visual form. For creating orbital diagrams, three rules are helpful.

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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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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.

According 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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Explanation:

Fermentation: When yeast is added to the dough, it begins to ferment the sugars present in the dough, producing carbon dioxide and ethanol. The carbon dioxide helps to leaven the dough, while the ethanol is mostly evaporated during baking.

Maillard reaction: During baking, the heat causes a reaction between the amino acids and sugars in the dough, producing a wide range of compounds that give bread its characteristic flavor and aroma. This reaction is known as the Maillard reaction.

Protein denaturation: The heat of baking causes the proteins in the dough to denature, or lose their native conformation. This helps to give bread its texture and structure, and also contributes to the development of its crust.

n specifies B. The energy and average distance from the nucleus, l specifies C. The subshell - orbital shape, ml specifies A. The orbital orientation.

n is known Principal quantum number

l is known Azimuthal quantum number

ml is known Magnetic quantum number

The energy and usual distance from the nucleus are described by the fundamental quantum number, or n.

The subshell and orbit's shape are described by the orbital quantum number, or l.

The orbit's direction is described by the magnetic quantum number, ml.

So, n specifies B. The energy and average distance from the nucleus.

l specifies C. The subshell - orbital shape.

ml specifies A. The orbital orientation.

Thus, n specifies B., l specifies C., ml specifies A.

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Compared to the atomic arrangement of atoms in diamond, the atomic arrangement of atoms in the ultra-light material were option B: spread apart, chaotic, and spongy.

The atomic arrangement of atoms in the ultra-light material described in the question is likely to be different from that of diamond. Diamond is a very hard and rigid material, with a highly ordered and crystalline atomic structure.

In contrast, the ultra-light material is described as being "spread apart, chaotic, and spongy," which suggests that its atomic arrangement is much less organized and more disordered than that of diamond.

Therefore, based on the above, this may be due to the use of a different type of bonding between atoms, or a different arrangement of atoms within the material, which results in a less rigid and more flexible structure.

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Answer: Diurnal temperature range is the difference between __maximum______ and ____minimum____ temperature each ___1 day______.

Explanation:

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.

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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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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-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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The amount of water needed to be added to prepare the solution would be 0.94 liters.

When diluting solutions, the number of moles of solutes before dilution must be equal to the number of solutes after dilution. The only thing that changes are the volume and concentration.

Thus, the equation of dilution is:

[tex]m_1v_1[/tex] = [tex]m_2v_2[/tex]

Where

In this case:

[tex]m_1[/tex] = 5 M, [tex]m_2[/tex] = 0.3 M, and [tex]v_2[/tex] = 1000 mL

Substituting:

5[tex]v_1[/tex] = 0.3 x 1000

    [tex]v_1[/tex] = 300/5

        = 60 mL

This means that the volume of the stock solution to be taken is 60 mL. The amount of water to be added would then be:

1000 - 60 = 940 mL

940 mL = 0.94 L

In other words, the amount of water needed to be added to prepare 1000 mL of 0.3M NaCl from a 5 M NaCl stock solution is 0.94 L.

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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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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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If XeF2 is polar or nonpolar based on the Lewis Structure and the molecular geometry (shape).

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Answer:

Gravity

Explanation:

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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Answer: The answer is false

Explanation:

The rate of effusion of substance A is 3 times the rate of effusion of substance B, and molar mass of A is 4g/mol, then molar mass of B is 36g/mol.

Graham Law:

The rate of effusion of a gaseous substance is inversely proportional to the square root of its molar mass. This is called Graham's Law

R = k/√M

where k is constant and m is molar mass of the substance.

rate of effusion of substance A is 3 times the rate of effusion of substance B.

molar mass of substance A is 4.00g/mol

Ra = 3Rb

Ra/Rb = √Mb/√Ma

3Rb/Rb = √Mb/√4

3 = √Mb/2

√Mb = 6

Mb = 36

so, molar mass of substance B is 36g/mol.

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Potassium fluoride and sodium hydroxide react to produce potassium hydroxide and sodium fluoride respectively. Option 2.

Potassium fluoride and sodium hydroxide undergo a double decomposition reaction. They exchange radicals to produce potassium hydroxide and sodium fluoride respectively according to the following equation:  

[tex]KF + NaOH --- > KOH + NaF[/tex]

Potassium is able to displace sodium from sodium hydroxide because it is higher on the reactivity series of metals than sodium.

Thus, the product of the reaction of potassium fluoride and sodium hydroxide are [tex]KOH[/tex] and [tex]NaF[/tex].

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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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Protein synthesis is a process that is generated within cells where different organelles and genetic components are involved through which proteins are generated.

The biosynthesis of proteins will be given by different parts, beginning with the translation of the genetic material. It will be given by different steps:

1. mRNA binds to ribosomes and the aminoacyl-tRNA to be associated to the first codon of the mRNA is associated.

2. The elongation of the polypeptide chain occurs, in which the amino acids are joined

3. The elongation is finished when the termination codons are reached.

4. The translation components are released and post-translational modifications are started.

5. The folding, glycosylation and modification of amino acids occur

6. Finally, the protein is released to generate its function

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Potential Energy is the form of energy contained in dam.

Total energy:

The total energy of each considered object is the sum of its potential energy (P.E) and kinetic energy (K.E) and is constant throughout motion. For example, at finite height, a ball has maximum potential energy and zero kinetic energy, and when released, K.E increases and becomes maximum at ground level, and P.E decreases to zero at ground level. , so the total energy increases. There is movement of the ball in the same way everywhere. The energy that an object has due to its motion is called kinetic energy, and the energy that an object has due to its position and shape is called potential energy.

Here the water dammed by the dam has a certain potential height. This means that water has latent energy because it is located far from the bottom. Therefore, water dammed up by a dam has potential energy.

Potential Energy:

In physics, potential energy is the energy possessed by an object due to its position relative to other objects, its own tension, electrical charge, or other factors. Common types of potential energy are the gravitational potential energy of a body, the elastic potential energy of an extended spring, and the electrical potential energy of an electric charge in an electric field. The unit of energy in the International System of Units (SI) is the joule, and the symbol is J.

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The concentration measures will change in value as the temperature of a solution changes is molarity. The correct option is 4.

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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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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The amount, in moles, of chlorine that would be present in 3 moles of [tex]MgCl_2[/tex] would be 6 moles.

[tex]MgCl_2[/tex] is made from magnesium and chlorine molecules according to the following equation:

[tex]MgCl_2 --- > Mg^{2+} + 2Cl^-[/tex]

From the above equation, 1 mole of [tex]MgCl_2[/tex] is made up of 1 mole of Mg and 2 moles of Cl.

Following this established ratio, the amount of chlorine that would be present in 3 moles of  [tex]MgCl_2[/tex] can be calculated as follows:

1 mole [tex]MgCl_2[/tex] = 2 moles of Cl

3 moles  [tex]MgCl_2[/tex] = 2 x 3/1

                           = 6 moles of Cl

In other words, 6 moles of Cl would be present in 3 moles of [tex]MgCl_2[/tex].

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