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3 years ago

Which of the following would have the largest pKa?

Chemistry

1 answer:

garri49 [273]3 years ago

5 0

Answer:

CH3CH2NH3+/CH3CH2NH2 would have the largest pKa

Explanation:

To answer this question we must know Kb of CH3CH2NH2 is 5.6x10⁻⁴, and for C6H5NH2 is 4.0x10⁻¹⁰. And the CH3CH2NH3+ and C6H5NH3+ are related with these substances because are their conjugate base. That means:

pKa of CH3CH2NH3+ = CH3CH2NH2; C6H5NH3+ = C6H5NH2

Also, Kw / Kb = Ka

Thus:

pKa of CH3CH2NH3+/CH3CH2NH2 is:

Kw / kb = Ka = 1.79x10⁻¹¹

-log Ka = pKa

pKa = 10.75

pKa of C6H5NH3+/ C6H5NH2 is:

Kw / kb = Ka = 2.5x10⁻⁵

-log Ka = pKa

pKa = 4.6

That means CH3CH2NH3+/CH3CH2NH2 would have the largest pKa

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Calculate the number of grams of sodium chloride in the solution. (Hint: Remember that sodium chloride is a strong electrolyte.)

creativ13 [48]

The question is incomplete, here is the complete question:

A solution contains 0.115 mol $H_2O$ and an unknown number of moles of sodium chloride. The vapor pressure of the solution at 30°C is 25.7 torr. The vapor pressure of pure water at this temperature is 31.8 torr. Calculate the number of grams of sodium chloride in the solution. (Hint: Remember that sodium chloride is a strong electrolyte.)

<u>Answer:</u> The mass of sodium chloride in the solution is 0.714 grams

<u>Explanation:</u>

The formula for relative lowering of vapor pressure will be:

$\frac{p^o-p_s}{p^o}=i\times \chi_{\text{solute}}$

where,

$p^o$ = vapor pressure of solvent (water) = 31.8 torr

$p^s$ = vapor pressure of the solution = 25.7 torr

i = Van't Hoff factor = 2

$\chi_{\text{solute}}$ = mole fraction of solute (sodium chloride) = ?

Putting values in above equation, we get:

$\frac{31.8-25.7}{31.8}=2\times \chi_{NaCl}\\\\\chi_{NaCl}=0.0959$

Mole fraction of a substance is calculated by using the equation:

$\chi_A=\frac{n_A}{n_A+n_B}$

$\chi_{\text{NaCl}}=\frac{n_{\text{NaCl}}}{n_{\text{NaCl}}+n_{\text{water}}}$

We are given:

Moles of water = 0.115 moles

$0.0959=\frac{n_{\text{NaCl}}}{n_{\text{NaCl}}+0.115}\\\\n_{\text{NaCl}}=0.0122mol$

To calculate the mass for given number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$

Moles of NaCl = 0.0122 moles

Molar mass of NaCl = 58.5 g/mol

Putting values in above equation, we get:

$0.0122mol=\frac{\text{Mass of NaCl}}{58.5g/mol}\\\\\text{Mass of NaCl}(0.0122mol\times 58.5g/mol)=0.714g$

Hence, the mass of sodium chloride in the solution is 0.714 grams

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3 years ago

What is a paragraph to fit this

german

Answer:

They add carbon Dioxide into the air warming the atmosphere which adds to the greenhouse effect, Making the temperature higher

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3 years ago

Propane, C3H8, consists of ________________ bonds and it can be expected to dissolve in hexane and to not dissolve in water.

PtichkaEL [24]

Non-polar covalent

Explanation:

Propane is made up of non-polar covalent bonds and it can be expected to dissolve in hexane and to not dissolve in water.

Propane is an hydrocarbon gas.

It forms by sharing of electrons between two atoms with very low electronegativity differences.

This differences results in equal sharing of the shared electron. Therefore they form a non-polar covalent bond.

Water is a polar covalent compound and cannot dissolve compounds that are not polar like propane.

Propane will only dissolve in a like substance like hexane which is equally non-polar.

learn more:

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3 years ago

What is the number of electrons in oxygen

Semmy [17]

Answer for your question is;

2,6 = 8
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6 0

2 years ago

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Enthalpies of reaction calculated from bond energies and from enthalpies of formation are often, but not always, close to each o

jolli1 [7]

The enthalpy change in a reaction is given by-

ΔH°rxn = ∑nΔH°f,products - ∑nΔH°f,reactants

This can be expressed in terms of bond energy as-

ΔH°rxn = BEreactants - BEproducts

Therefore, the calculated bond energy according to the above equation will be-

ΔH°rxn = [ (C-C) + 2(C-O) + 4(C-H) + 2(O-H) ] - [ (C-C) + 2(C-O) + 4(C-H) + 2(O-H) = 0 kJ/mol

<h3>What is enthalpy change?</h3>

Enthalpy change is a measure of the energy emitted or consumed in a reaction. This can be determined using the following equation which involves standard enthalpy of reactant and product formation:

ΔH°rxn = ∑nΔH°f,products - ∑nΔH°f,reactants

<h3>What is bond energy?</h3>

Bond energy is defined as the amount of energy needed to dissociate a mole of molecules into their individual atoms.

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