Chemistry Multiple choice help? Compare answers! 4 questions. ?

Question

1. The Kb for NH3(aq) is:

A) -5.8 E 10^-10 

B) 1.0 E 10^-14 

C) 1.7 E 10^-5 

D) 1.7 E 10^ 9

E is supposed to look fancy and curly, I don’t remember what it’s supposed to be called. Anyway, C?

2. Which of the following is a correct statement concerning an aqueous solution? 

A) As [H3O+ (aq)] increases, [OH (aq)] decreases.

B) As [H3O+ (aq) big] increases, [OH (aq)] increases. 

C) As pH increases, [OH - (aq)] decreases. 

D) As pH increases , [H3O+ (aq)] increases.

Is it D?

3. You have been given two unlabelled acidic solutions. One is a weak acid and one is a strong acid, but they have the same pH. Which of the following statements about the two acids is true?

A) The weak acid more easily releases hydrogen ions and is more concentrated than the strong acid. 

B) The strong acid more easily releases hydrogen ions and is more concentrated than the weak acid. 

C) The weak acid more easily releases hydrogen ions and is less concentrated than the strong acid. 

D) The strong acid more easily releases hydrogen ions and is less concentrated than the weak acid.

4. When citric acid combines with water in the mouth, one reaction that occurs is: 

H3Ct (aq) + H2O (l) H2Ct- (aq) + H3O+ (aq) 

The conjugate acid-base pairs in this equation are...

A) H3Ct (aq) / H 3 O+ (aq) and H2O (l) / H2Ct- (aq) 

B) H3Ct (aq) / HCt^2- (aq) and H3O+ (l) / H2O (l)

C) H3Ct (aq) / H 2 O (l) and H3O+ (aq) / H2Ct- (aq) 

D) H3Ct (aq) / H 2 Ct (aq) and H3O+ (l) / H2O (l)

Answer 1

Favorite Answer

1.

Refer to: http://wiki.chemprime.chemeddl.org/articles/t/a/b/...

Kb for NH₃ = 1.8 × 10⁻⁵

The answer: C) 1.7 × 10⁻⁵

(the closest answer)

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2.

A) true

Kw = [H₃O⁺(aq)] [OH⁻(aq)] = 1.0 × 10⁻¹⁴

As [H₃O⁺(aq)] increases, [OH⁻(aq)] decreases.

B) false

Refer to the explanation of option A).

C) false

pH = -log[H₃O⁺(aq)]

As pH increases, [H₃O⁺(aq)] decreases. Hence, [OH⁻(aq)] increases.

D) false

Refer to the explanation in part C).

The answer: A) As [H₃O⁺(aq)] increases, [OH⁻(aq)] decreases.

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3.

A strong acid completely ionizes in water to form hydrogen ions, while a weak acid partially ionizes in water to form hydrogen ions.  Obviously, the strong acid more releases hydrogen ions. Hence, A) and C) are false.

When two acids have the same pH, their concentration of hydrogen ions are the same. As the weak acid less easily releases hydrogen ions, the weak acid must be more concentrated. Hence, B) is false.

The answer: D) The strong acid more easily releases hydrogen ions and is less concentrated than the weak acid.

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4.

The reactions of the two acid-base pairs:

H₃Ct(aq) → H₂Ct⁻(aq) + H⁺(aq)

H₂O(ℓ) + H⁺(aq) → H₃O⁺(aq)

The answer: D) H₃Ct(aq) / H₂Ct⁻(aq) and H₃O⁺(aq) / H₂O(ℓ)

(There are some typos in the options of the question.)

Answer 2

1) C) 1.7 E 10^-5 

2) No is not D, When pH is increasing is because OH- is increasing. A high pH is considered to be very basic not acid. I will go with Answer A.

3) B) The strong acid more easily releases hydrogen ions and is more concentrated than the weak acid. 

4) C) H3Ct (aq) / H 2 O (l) and H3O+ (aq) / H2Ct- (aq)