Chemistry

Just some homework. Would like to know if I am right, thanks.

1. Adding salt of a weak acid to a solution of the weak acid:
a)lowers the concentration of the nonionized acid and the concentration of the H30+
b)lowers the concentration of the nonionized acid and raises the concentration of the H30+
c)raises the concentration of the nonionized acid and the concentration of the H30+
d)raises the concentration of the nonionized acid and lowers the concentration of the H30+

I chose c.

2. Salts of a weak acid and stong base produce solutions that are:
acidic, basic, neautral, or all 3?

I said all 3.

3. If an acid is added to a solution of a weak base and it's salt,
a)more water is formed and more weak base ionizes
b) hydronium-ion concentration decreases
c) more hydroxide ion is formed
d) more nonionized weak base is formed

b?

4. Label 2 conjugate acid-base pairs as acid 1, acid 2, base 1 and base 2:

a) CO3 + H3O->HCO3 + H2O

b)HPO4+H2O->OH+H2PO4

I'm not really sure how to do this at all, I just know that the ones begiining with "h" are acids..

Part 2: Which reaction in part a) is hydrolysis?

Part 3: As the first reaction in part a) proceeds, the pH of the solution increases, decreases, or stays at the same level?

-I would guess decreases, because the water neitralizes it...I don't know, though. Thanks.

What kind of a class is this? These questions can't be answered with just a smattering of a knowledge of chemistry. For a "guess the right answer" type, these are fairly sophisticated.

1. Adding salt of a weak acid to a solution of the weak acid:
a)lowers the concentration of the nonionized acid and the concentration of the H30+
b)lowers the concentration of the nonionized acid and raises the concentration of the H30+
c)raises the concentration of the nonionized acid and the concentration of the H30+
d)raises the concentration of the nonionized acid and lowers the concentration of the H30+

I chose c.

For a weak acid, which I will call HA, it ionizes this way.
HA ==> H^+ + A^-
The sodium salt, NaA, would increase A^-. According to Le Chatelier's Principle, the reaction will shift in such as way as to relieve the stress placed on the equilibrium. In this case, the reaction will shift to the ?LEFT because that is the way to use up the added A^-. So, H^+ will decrease and HA will increase. Of the answers listed, d is the correct one.


2. Salts of a weak acid and stong base produce solutions that are:
acidic, basic, neautral, or all 3?

I said all 3.
Let's choose a salt of a weak acid and a strong base. We might choose a weak acid, such as acetic acid, which I will call HAc, and a strong base such as NaOH. That will produce the salt which is a salt of a weak acid and a strong base. Think about what happens when NaAc hydrolyzes in water.
NaAc + HOH ==> NaOH + HAc. I have taken some liberties with the equation (for example, Na doens't hydrolyze). So the solution will be basic. Common sense tells you that a strong base and weak acid will be basic.


3. If an acid is added to a solution of a weak base and it's salt,
a)more water is formed and more weak base ionizes
b) hydronium-ion concentration decreases
c) more hydroxide ion is formed
d) more nonionized weak base is formed

b?
I am a little confused by the answers. If we take a weak base, such as NH3, and a salt of the weak bsse, such as NH4^+, the addition of a strong acid to that (HCl for example) will cause the NH3 to form more NH4^+ and more H2O will be formed. That is answer a. But answer c is correct, too, although OH^- won't increase much.

4. Label 2 conjugate acid-base pairs as acid 1, acid 2, base 1 and base 2:

a) CO3 + H3O->HCO3 + H2O

b)HPO4+H2O->OH+H2PO4

I'm not really sure how to do this at all, I just know that the ones begiining with "h" are acids..

Part 2: Which reaction in part a) is hydrolysis?

Part 3: As the first reaction in part a) proceeds, the pH of the solution increases, decreases, or stays at the same level?

-I would guess decreases, because the water neitralizes it...I don't know, though. Thanks.

For these questions, I will refer you to your notes/ text where you should read about the Brosted-Lowry theory of acids and bases. All of this will be discussed there.

Thanks...as to your question, it's an advanced Chemistry class, if that's what you mean...he just moves so fast sometimes, that we get through a few chapters a day. It's hard to keep up. :[

OK. Then the explanations I gave were not too technical for you to understand.

Not at all. I can understand it just fine if it's in front of me with a split second to comprehend it...thank you.

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