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Questions on Acids and Bases

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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.

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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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See Also This Related BrainMass Solution

Acid, Bases, Equilibria Questions

1) The solvent cation in liquid ethanol, CH3CH2OH, is

a) CH3CH2O- b) H+ c) CH3CH2OH+ d) CH3CH2OH2+ e) CH3CH2OH-

Answer _________

2) Fill in the blanks.

a) the normality of 0.20M solution of H2SO4 ________________________

b) The following reaction is best classified as an Arrhenius, Bronsted or Lewis acid base reaction? SiF4 + 2F- --- SiF62- _________________

c) The conjugate base of H2PO3- _________________________

d) The conjugate acid of AsH3 _________________________

3) Identify the correct answer in each case.

a) The stronger acid, H3SbO3 or H3AsO3 ? _____________________

b) The stronger base, GeH4 or SiH4 ? ________________________

c) The stronger acid, H2TeO3 or H2 TeO4 ? _______________________

d) The stronger base, Pd (OH)2 or Sn (OH)2 ? _________________________

e) The stronger conjugate acid, the conjugate acid of Cl04- or the conjugate acid of MnO4-? ____________________________

f) The amphiprotic species in the following equation

H2CO3 -- H+ + HCO3- _____________________

g) The conjugate base in the Bronsted - Lowry reaction
HBr + NH3 - NH4+ + Br- _______________________

h) The Lewis base in the reaction
Cu(NO3)2 + 4H2O - Cu(H2O)42+ + 2NO3- ____________________

4. In a 0.90M solution of the weak acid HA, the acid is 11% ionized. What is the ionization constant, Ka, for the acid? (Show work)

5. Ka for HC2H3O2 is 1.8 x 10-5. To adjust the pH value of one liter of 0.020M acetic acid to pH = 6.0, one must add how many grams of KC2H3O2? (Show work)

6. Would the pH of a 0.1M solution of Cs2SO3 be less than, greater than, or equal to 7.0? (Show work)

7. In the titration of HClO4 with LiOH, 50.0mL of 0.35OM LiOH is added to 30.0mL of 0.400M HCl04. What is the pH at this point in the titration? (Show work)

8. What is the pH of a buffer made by mixing equal volumes of 0.10M NH3 and 0.10M NH4Cl? Kb for NH3 = 1.8 x 10-5
(Show work)

9. What is the pH after this same solution is made 0.020M in KOH? (Show work)

10. Below a pH of 4.8, an indicator, exists in the blue acid form, HIn. At pH 4.8 about 10% of the indicator exists in the rose base form. What is the ionization constant of this indicator? (Show work)

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