# Homework Help: One of these is wrong

1. Sep 19, 2008

### Banaticus

1. The problem statement, all variables and given/known data
On a recent chemistry exam, there were 15 multiple choice problems. I missed one of them. I was certain that I was right on every problem, except one problem that I guessed on. After comparing my test with the test of other students, though, I apparently guessed correctly on that one problem. So, one of those questions that I was sure about is apparently incorrect. Which question did get wrong?

3. The attempt at a solution
1. Which of the following combination of names and formulas is incorrect?
• sodium hydroxide -- NaOH
• iron(III) chloride -- $FeCl_2$
• potassium permanganate -- $KMnO_4$
[*]lithium carbonate -- $LiCO_3$ I said it should be $Li_2CO_3$
• nitric acid -- $HNO_3$
2. How many significant figures are in the value 0.0003060000?
I said 7.
3. Which of the following element/family names is incorrect?
• Na = Alkali metal
• F = Halogen
[*]Ba = Transition Metal I said that Ba is not a transition metal
• H = Non-metal
• Xe = Noble gas
4. When the equation $C_4H_{10}+O_2\rightarrow CO_2+H_2O$ is balanced with the smallest set of integers, the sum of the coefficients is:
I thought it should be balanced as: $2C_4H_{10}+13O_2\rightarrow 8CO_2+10H_2O$, 2+13+8+10=33
5. Superman comes from the planet Krypton. If you have 0.00789 g of the gaseous element Krypton, how many moles does this represent?
I said: .00789 g / 83.8 g/mol = $9.41 x 10^{-5}$
6. When the equation $C_5H_6N_2OS+O_2\rightarrow CO_2+H_2O+N_2+SO_2$ is balanced with the smallest set of integers, the sum of the coefficients is:
I thought it should be balanced as: $C_5H_6N_2OS+7O_2\rightarrow 5CO_2+3H_2O+N_2+SO_2$ = 1+7+5+3+1+1=18
7. The anesthetic... The compound is packaged as a 10% solution (by mass) in water. If your dentist injects 0.50 mL of the solution, what mass of procaine hydrochloride (in mg) is injected? Assume the density of the solution is 1.0 g/mL.
8. An isotope, X, of a particular element has an atomic number of 6 and a mass element of 14. Therefore,
9. Succinic acid occurs in fungi and lichens. Its empirical formula is $C_2H_3O_2$ and its molar mass is 118.1 g/mol. What is its molecular formula?
10. Which one of the following combinations of names and formulas of ions is incorrect?
11. Which combination represents a $^{57}Fe^{2+} ion? 12. Pepto-Bismol... contains 300 mg of bismuth subsalicylate, [itex]C_{21}H_{15}Bi_3O_{13}$ per tablet. What is the molar mass of this compound?
13. The mass in grams of one molecule of dinitrogen trioxide is approximately:
14. Which of the following as the largest number of protons?
15. A red glaze on percelain can be produced by using MnSO_4. What is its name?

2. Sep 19, 2008

### GCT

The one's that you answered seem fine , you have yet to display your answers for the others.

3. Sep 19, 2008

### Staff: Mentor

Typo?

4. Sep 20, 2008

### Banaticus

I don't have the test anymore, so I can't go look at that Fe one, but I figured out what I missed. #7 asked for the answer in mg and I gave the answer in g and somehow missed the mg right by the number. ;)

My teacher allows us to turn a test back right after we get the graded test back, for a few bonus points if we rework every problem that we got wrong (in an attempt to get us to learn why we got certain questions wrong and what we could have done differently), as least as far as the workout problems go. All of the multiple choice questions are lumped together as "one question", so to get the points you have to go through, figure out what you missed and why you missed it.