CHEM 105 - FINAL REVIEW EXAM
QUESTIONS & ANSWERS
Which calculation of experimental data has the correct number of significant figures in
the results?
a. (3.2-1.10)/3.664 = .573
b. (12.4-5.71)/2.11 = 3.2
c. (15.8-5.26)/8.47 = 1.2
d. (12.735-2.221)/3.85 = 2.736 - Correct Answers -B!
Why?
because when you minus (12.4-5.71) you get the decimal place to be in the ones
decimal place.
A phosphorus ion with a mass number of 32 and charge -3 how many electrons?
a. 35
b. 29
c. 18
d. 13 - Correct Answers -C!
Why?
because you aren't concern with mass number, you are concerned with the atomic
number. Protons = electrons and the atomic number of phosphorus is 15. However,
when the charge is -3 you add 3 to whatever the atomic number is
so the answer is 15+3=18
Which formula is incorrectly paired with its name?
a. NaHCO3 sodium hydrogen carbonate
b. BaSO3 barium sulfate
c. KH potassium hydride
d. Cu(NO3)2 copper(II) nitrate - Correct Answers -B!
Why?
BaSO3 is barium SULFITE not SULFATE
,SO3= sulfite
SO4 = sulfate
What is the formula for gold cyanate when magnesium cyanate has the formula
Mg(OCN)2 and gold sulfate has the formula Au2(SO4)3?
a. Au2(OCN)2
b. Au(OCN)3
c. Au(OCN)2
d. Au3OCN - Correct Answers -B!
Why?
Because Au has a charge of 3, and OCN has a charge of 1 thus you would just switch
the charge of the two compounds.
The missing ion below belongs in which family?
Al(3+) Sr(2+) ? Cl(-) Se(2-) N(3-)
a. halogens
b. noble gases
c. alkali metals
d. alkaline earth metals - Correct Answers -C!
Why?
Because Al is grouped into other metals
Sr is grouped into Alkaline Earth metals
Cl is grouped into Halogens
Se is grouped into Chalocogens
N is grouped into Non-metals
Therefore, the choice remains between noble gases and alkali metals.
The choice should be Alkali Metals dues to the fact that Noble gases do not form ions
as easily as the other groups.
How many moles of nitrogen gas (N2) could be produced in the complete
decomposition of 2.50 moles of TNT, C7H5N3O6
a. 1.25
b. 3.00
c. 3.75
d. 7.50 - Correct Answers -C!
Why?
Because you would do this conversion,
2.50 moles of TNT x (3 N/ 2 N)
, because there is 2 N's in N2
How many grams of carbon are contained in 2.50 moles of TNT, C7H5N3O6?
a. 4.29
b. 30.0
c. 84.1
d. 210. g - Correct Answers -D!
Why?
because you would do this conversion
2.50 moles of TNT x (7 mol of C/ 1 mol of TNT) x
(12.0107 MM of C/ 1 mol of C) = 210 grams
A compound containing only phosphorus and sulfur is used in matches. What is the
empirical formula of this compound given that a 10 g sample of the compound contains
5.629 g of phosphorus?
a. P4S3
b. P2S5
c. P2S3
d. PS4
e. P5S4 - Correct Answers -A
Why?
Because first you would (10g-5.629g) = 4.371 g of Sulfur
Then you would
5.629 g x (1 mol/ 30.9738 MM) = .182 mol of P
4.371 g x (1 mol/ 32.066 MM) = .125 mol of S
.182/.125 = 1.45, so you would have to multiply this by three to get it closer to an even
number = P4
.125/.125 = 1, since you multiplied P by three you also have to multiply this one by three
as well
= P4S3
When the equation below is balanced with whole number coefficients, what is the
coefficients of carbon dioxide?
C4H10(g) + O2(g) = CO2(g) + H2O(g)
QUESTIONS & ANSWERS
Which calculation of experimental data has the correct number of significant figures in
the results?
a. (3.2-1.10)/3.664 = .573
b. (12.4-5.71)/2.11 = 3.2
c. (15.8-5.26)/8.47 = 1.2
d. (12.735-2.221)/3.85 = 2.736 - Correct Answers -B!
Why?
because when you minus (12.4-5.71) you get the decimal place to be in the ones
decimal place.
A phosphorus ion with a mass number of 32 and charge -3 how many electrons?
a. 35
b. 29
c. 18
d. 13 - Correct Answers -C!
Why?
because you aren't concern with mass number, you are concerned with the atomic
number. Protons = electrons and the atomic number of phosphorus is 15. However,
when the charge is -3 you add 3 to whatever the atomic number is
so the answer is 15+3=18
Which formula is incorrectly paired with its name?
a. NaHCO3 sodium hydrogen carbonate
b. BaSO3 barium sulfate
c. KH potassium hydride
d. Cu(NO3)2 copper(II) nitrate - Correct Answers -B!
Why?
BaSO3 is barium SULFITE not SULFATE
,SO3= sulfite
SO4 = sulfate
What is the formula for gold cyanate when magnesium cyanate has the formula
Mg(OCN)2 and gold sulfate has the formula Au2(SO4)3?
a. Au2(OCN)2
b. Au(OCN)3
c. Au(OCN)2
d. Au3OCN - Correct Answers -B!
Why?
Because Au has a charge of 3, and OCN has a charge of 1 thus you would just switch
the charge of the two compounds.
The missing ion below belongs in which family?
Al(3+) Sr(2+) ? Cl(-) Se(2-) N(3-)
a. halogens
b. noble gases
c. alkali metals
d. alkaline earth metals - Correct Answers -C!
Why?
Because Al is grouped into other metals
Sr is grouped into Alkaline Earth metals
Cl is grouped into Halogens
Se is grouped into Chalocogens
N is grouped into Non-metals
Therefore, the choice remains between noble gases and alkali metals.
The choice should be Alkali Metals dues to the fact that Noble gases do not form ions
as easily as the other groups.
How many moles of nitrogen gas (N2) could be produced in the complete
decomposition of 2.50 moles of TNT, C7H5N3O6
a. 1.25
b. 3.00
c. 3.75
d. 7.50 - Correct Answers -C!
Why?
Because you would do this conversion,
2.50 moles of TNT x (3 N/ 2 N)
, because there is 2 N's in N2
How many grams of carbon are contained in 2.50 moles of TNT, C7H5N3O6?
a. 4.29
b. 30.0
c. 84.1
d. 210. g - Correct Answers -D!
Why?
because you would do this conversion
2.50 moles of TNT x (7 mol of C/ 1 mol of TNT) x
(12.0107 MM of C/ 1 mol of C) = 210 grams
A compound containing only phosphorus and sulfur is used in matches. What is the
empirical formula of this compound given that a 10 g sample of the compound contains
5.629 g of phosphorus?
a. P4S3
b. P2S5
c. P2S3
d. PS4
e. P5S4 - Correct Answers -A
Why?
Because first you would (10g-5.629g) = 4.371 g of Sulfur
Then you would
5.629 g x (1 mol/ 30.9738 MM) = .182 mol of P
4.371 g x (1 mol/ 32.066 MM) = .125 mol of S
.182/.125 = 1.45, so you would have to multiply this by three to get it closer to an even
number = P4
.125/.125 = 1, since you multiplied P by three you also have to multiply this one by three
as well
= P4S3
When the equation below is balanced with whole number coefficients, what is the
coefficients of carbon dioxide?
C4H10(g) + O2(g) = CO2(g) + H2O(g)
