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Questions on Acids and Bases

1- What is the difference between a strong acid and a weak acid? Choose from:
A strong acid is dangerous to human health, a weak acid is not.
A strong acid dissociates completely in solution, while a weak acid only dissociates partway.
A strong acid will neutralize a base, but a weak acid isn't strong enough to do so.
A weak acid will not add protons to solution.

2- What is the H + concentration for an aqueous solution with pOH = 4.21 at 25 ∘ C ?

3- Arrange the following aqueous solutions, all at 25 ∘ C, in order of decreasing acidity.(ph=5.45,0.0023 M HCl, pOH=8.55, 0.0018 M KOH)

4- At a certain temperature, the pH of a neutral solution is 7.79. What is the value of K w at that temperature?

5- Calculate [H30+] in each aqueous solution at 25 C and classify each solution as acidic or basic one.

[OH − ]= 5.2×10−4M Express your answer using two significant figures.
OH − ]= 1.9×10−12M Express your answer using two significant figures.

6- 0.45g of hydrogen chloride (HCl ) is dissolved in water to make 5.5Lof solution. What is the pH of the resulting hydrochloric acid solution? Express the pH numerically to two decimal places.

7- 0.25g of sodium hydroxide (NaOH ) pellets are dissolved in water to make 7.0L of solution. What is the pH of this solution? Express the pH numerically to two decimal places.

8- What assumption is commonly used to simplify the process of finding the pH for a solution of a weak acid? Choose from:

~The quadratic equation is the fastest way to find the pH of a weak acid, and the assumption is that the quadratic equation will work.
~For many weak acid solutions, it is assumed that [H3O+] is small relative to the initial concentration of acid, so the "x is small" approximation is used.
~The concentration of H3O+ is assumed to be directly found from the Ka expression, so all that is needed is to plug the initial concentrations of each species into the Ka expression.
~The concentration of H3O+ in solution is assumed to be equal to the concentration of the weak acid.

9- A certain weak acid, HA , has a K a value of 8.5×10−7. Calculate the percent ionization of HA in a 0.10 M solution. Express your answer to two significant figures and include the appropriate units. Calculate the percent ionization of HA in a 0.010 M solution. Express your answer to two significant figures and include the appropriate units.

10- What mass of HClO 4 should be present in 0.600L of solution to obtain a solution with each pH ?

pH = 2.50 Express your answer using two significant figures.
pH = 1.50 Express your answer using two significant figures.

11- A 0.115M solution of a weak acid (HA ) has a pH of 3.31. Calculate the acid ionization constant (K a ) for the acid. Express your answer using two significant figures.

12- Find the pH of a 0.150M solution of a weak monoprotic acid having K a = 1.6×10−5. Express your answer to two decimal places.

13- Find the percent ionization of a 0.150M solution of a weak monoprotic acid having K a = 1.6×10−5. Express your answer using two significant figures.

Solution Preview

Chapter 15 (Acids and Bases) Questions
1- Strong acids dissociate completely while weak acids do not.

2- [H+] = 10^(-pH) = 10^(-(14-4.21)) = 10^(-9.79) = 1.62 x 10^(-10) M

3- As pH increases, the acidity decreases. Hence the order is, 0.0023 M HCl > pH 5.45 = pOH 8.55 > 0.0018 M KOH

4- [H+] = [OH-] for a neutral solution.
[H+] = 10^(-pH) = 1.6 x 10^-8 M
Kw = [H+]{OH-] = 2.63 x 10^-16

5-
[OH − ]= 5.2×10−4M Express your answer using two significant figures.
[H3O+] = 1.00 x 10^-14 / (5.2 x 10^-4) = 1.9 x 10^-11 M

OH − ]= 1.9×10−12M Express your answer using two significant figures.
[H3O+] = 1.00 x 10^-14 / (1.9 x 10^-12) = 5.3 x 10^-3 M

6- [H+] = moles HCl / Vol = (0.45 / 36.46) / 5.5L = 0.00224M
pH = ...

Solution Summary

The differences between a strong acid and a weak acid are provided. The expert arranges the aqueous solutions for decreasing acidity.

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