To make a long story short, my youngest daughter decided to endure 
through 4 semesters of chemistry, and now is paying up for it. She is 
a talented little girl, but science is not her thing and it hurts for 
me to see her study so hard but understand so little. It runs in the 
family. I wanted to help myself, but me and my wife are no scientists 
at all, plus it was so long ago. Tutoring is very very weak at where 
she goes, and we know few friends around here who are capable of 
helping, most of which already are looking at us the wrong way for 
asking so much. I decided to open my pocket and let you, Chemistry 
folks, help us out. I secretly took the next set of questions from my 
daughters assignment section, and here they are. I understand that 
many (or most) of you would have the problem to giving direct help 
like this, "learning and understanding the material is the most 
important", right ? Wrong. Only but a few of you would understand the 
pain I feel when I see my daughter quietly cry in her room over her 
low assignment grades after hours and hours of studying daily. 
  
Below I copied down some of the questions and choice answers that came 
along. I tried my best to copy down everything number to number, word 
for word. Its a little bit difficult to transfer everything to text, 
but I tried. Please feel free to clarify if you did not understand a 
part. 
  
I am asking for a list of answers to the problems, in numerical + 
content format, as such : 
  
Question 1: Answer 3. The number of moles is 4.0.  
Question 2: Answer 5. The reaction is reversed.  
  
Time is an issue, but I would like the answers to be correct. I do not 
want to check my daughters answers and tell her that one of her 
correct answers is incorrect simply because what was given to me is a 
wrong answer. Once again I apologize for such rude question, but I am 
desperate, and I ran out of all other options. I am also considering a 
big tip for those who'll work hard on these, do all (or most) of the 
questions, provide the correct answers and hopefully as soon as 
possible. 
  
Thank you once more. You are my last hope. 



1) Which of the following salts is the most acidic
in aqueous solutions?

1. AgNO3
2. NaI
3. Pb(NO3)2
4. Fe(NO3)2
5. BaCl2
6. KBr
7. Al(NO3)3

2) Assume that fve weak acids, identifed only
by letters (A, B, C, D, and E), have the following 
ionization constants.

Acid           Ionization Constant Ka value

A              1.0 * 10^-3
B              3.0 * 10^-5
C              2.6 * 10^-7
D              4.0 * 10^-9
E              7.3 * 10^-11

A 0.10 M solution of which acid would have
the lowest pH?

1. acid A
2. acid B
3. acid C
4. acid D
5. acid E

3) Urine normally has a pH of 6.0. A
patient eliminates 1801 mL of urine per day.
How many moles of H3O+ are eliminated per
day?

1. 42 mol H3O+
2. 1.8 * 10^3 mol H3O+
3. 1.8 * 10^-6 mol H3O+
4. 1.8 * 10^-7 mol H3O+
5. none

4) Solution A has a H+ concentration of 10^-5 M.
Solution B has a H+ concentration of 10^-3 M.
Which one has a greater pH?
Which one contains more OH- ions?

1. B, B
2. A, A
3. B, A
4. A, B

5) What is the conjugate acid of water?

1. NH3
2. HCl
3. H3O+
4. H2O
5. OH-

Hello jwheel-ga!

I saw your series of questions and had a long debate with myself as to
whether or not I should answer them. As a parent I can respect what
you are doing in trying to assist your daughter in her studies. I hope
that as you share these answers and explanations with her she can gain
the reinforcement that she needs to learn this subject well.

Because of the urgency that you expressed I wanted to get these
answers out to you quickly. I do recommend that you find a local
university student or possibly a student who has recently completed
the same course who could serve as a tutor for your daughter.
One-on-one personal assistance could prove to be an invaluable tool in
your daughter’s learning.

With that said, here are the answers to this set of questions.

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Question 1: Answer 6. KBr is the strong acid.

The Shodor Foundation’s Chemistry website
(http://www.shodor.org/unchem/basic/ab/) states on its acid-base page
that there are only 7 “strong acids”:

HCl, HBr, HI, H2SO4, HNO3, HClO3, HClO3, HclO4

“Strong acid” means that the Hydrogen ion [H+] completely dissociates
from its conjugate anion.

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Question 2: Answer 1, Acid A has the lower pH.

The higher the Ka, the stronger the acid. A stronger acid will have a
higher concentration of H+, and therefore a lower pH. Since the
concentration of each acid is the same (.1 M) you can omit that in
your reasoning.

From The Net Equation at Thinkquest.org
(http://library.thinkquest.org/C004970/acidbase/concepts.htm)

“Both Ka and Kb are constants that express the acidity of a substance.
Large values for either Ka or Kb indicate a strong acid or base. If
the Ka for an acid is very high, the Kb for its conjugate base is very
small, and vice versa. The same is true for the Kb of a base and the
Ka of its conjugate acid.”

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Question 3: Answer 3. 1.8 x 10^-6 mol of H3O+ are excreted in 1801 ml
of urine.

If the pH is 6.0, then the H3O+ concentration is equal to 10^-6 mols/L
(remember, pH = -log[H+], where you can substitute H3O+ for H+). Then
determine the moles of H3O+ in 1801 ml, or 1.801 L of urine.

(10^-6 mols/L H3O+) x (1.801 L) = 1.8 x 10^-6

For a discussion of Moles and Molarity go to About.com
(http://chemistry.about.com/library/weekly/aa081302a.htm).

For more information on pH see the entry at Thinkquest.org
(http://library.thinkquest.org/C004970/acidbase/concepts.htm).

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Question 4: Answer 2. Solution A has both the higher pH and greater
concentration of OH-.

The Shodor Foundation again lists definitions for pH and defines it in
terms of the concentration of H+ and OH- ions.

pH = -log[H+], therefore solution A has a pH of 5 and solution B has a
pH of 3.

pOH = -log[OH-]. Since we don’t know the concentration of OH- ions yet
we need a formula that will help us determine it.

pH + pOH = 14.00

Solution A, pH = 5 so pOH = 9, therefore [OH-] = 10^-9
Solution B, pH = 3 so pOH = 11, therefore [OH-] = 10^-11

Solution A has a higher concentration of OH-.

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Question 5: Answer 3. H3O+ is the conjugate acid of water (H2O).

Using the Bronsted-Lowry equation, every acid has a conjugate base and
every base has a conjugate acid. They are defined as the following:

acid: anything that donates a [H+] (proton donor)
base: anything that accepts a [H+] (proton acceptor)

In the case of water, it dissociates according to the following
equation:

H2O + H2O < - - > OH- + H3O+

Therefore the conjugate acid (or proton donor) is the hydronium ion,
H30+

For further explanation of the Bronsted-Lowry equation, visit The
Columbia Encyclopedia entry on acid-base chemistry at:
http://www.slider.com/enc/1000/acids_and_bases_Acid-Base_Theories.htm

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I hope that these answers will help you as you assist your daughter in
her studies. Should anything be unclear, please let me know so I can
clarify it for you.

Good luck to you and your daughter!
 
Sincerely,
Boquinha-ga

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Google Search Strategy:
acid base chemistry equation
conjugate acid water
moles defined chemistry

And its you to the rescue again and again! If I were able to put 6
stars, I would. Thank you.

Thank you for the kind words, 5-star rating, and generous tip. I wish
you and your daughter the best!

Sincerely,
Boquinha-ga