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) What is the [(PO4)-3] in a solution made by
adding NaOH to a 0.20 M H3PO4 solution
until the pH = 11.00? (assume the volume
remains constant)
1. 0.072 M
2. 0.20 M
3. 0.15 M
4. 0.0034 M
5. 0.0069 M
2) Ka for HF is 7.2 * 10^-4 at 25deg Celcius.
What are the concentrations of H3O+ and
undissociated HF for a 0.05Msolution of HF?
(Solve full quadratic equation) The reaction is
HF + H2O --> H3O+ + F-
1. [H3O+] and [HF] = 5.7 * 10^-3 5.0 * 10^-2
2. [H3O+] and [HF] = 5.7 * 10^-3 3.9 * 10^-2
3. [H3O+] and [HF] = 2.7 * 10^-2 5.0 * 10^-2
4. [H3O+] and [HF] = 2.7 * 10^-2 2.3 * 10^-2
5. [H3O+] and [HF] = 5.7 * 10^-3 4.4 * 10^-2
3) The pH range of human blood plasma is 7.3 - 7.5.
After exercising, an athlete momentarily
reduces his blood pH. This reduction implies
a(n) _____________
1. basicity increase.
2. OH- concentration increase.
3. H+ concentration constant.
4. acidity increase.
5. H+ concentration decrease.
6. OH- concentration decrease.
4) A change in pH from 5 to 4 represents:
1. not enough information given
2. 10% less H+ ions in solution at pH 4 than
pH 5
3. 10% more H+ ions in solution at pH 4
than pH 5
4. 90% more H+ ions in solution at pH 4
than pH 5
5. 100% more H+ ions in solution at pH 4
than pH 5
5) HF is used to dissolve silicate rocks, HNO3 is
used to dissolve plants and HCl will dissolve
neither.
Which is considered a weak acid?
1. HNO3
2. HF
3. All are weak acids.... need to know Ka
4. None....all are strong acids values to determine the weakest.
5. HCl |
