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Honors Moles, % Composition, Empirical/Molecular Formula

Total questions: 40

Worksheet time: 53mins

Name
Class
Date
1.

What is the molar mass of CO (carbon monoxide)?

a)

12

b)

16

c)

38

d)

28

2.

How many iron, nitrogen and oxygen atoms are there in Fe(NO3)3?

a)

3 iron atoms, 3 nitrogen atoms and 6 oxygen atoms

b)

3 iron atoms, 3 nitrogen atoms and 9 oxygen atoms

c)

1 iron atom, 1 nitrogen atom and 3 oxygen atoms

d)

1 iron atom, 3 nitrogen atoms and 9 oxygen atoms

3.

What is the molar mass of Fe(NO3)3?

a)

118

b)

86

c)

214

d)

242

4.

Sodium reacts with chlorine to form sodium chloride.

__Na + Cl2 → 2NaCl

What is the missing number needed to balance the equation?

a)

1

b)

2

c)

3

d)

4

5.

Calculate the mass of 0.25 mol of carbon dioxide molecules.

a)

33 g

b)

11 g

c)

12 g

d)

16 g

6.

Calculate the number of moles of water molecules in 36 g of water.

a)

2 mol

b)

0.5 mol

c)

18 mol

d)

16 mol

7.

What is the relative formula mass of Mg(OH)2?

a)

41

b)

39

c)

42

d)

58

8.

How many moles of oxygen atoms are in 31.998 grams of oxygen?

To solve this problem you should...

a)

multiply by 1 mole6.022x1023\frac{1\ mole}{6.022x10^{23}}  

b)

multiply by  1 mole15.999 g\ \frac{1\ mole}{15.999\ g}  

c)

multiply by 6.022x10231 mole\frac{6.022x10^{23}}{1\ mole}  

d)

multiply by 15.999 g1 mole\frac{15.999\ g}{1\ mole}  

9.

How many moles of oxygen atoms are in 3.011 x 10^23 atoms of oxygen?

To solve this problem you should...

a)

multiply by 1 mole6.022x1023\frac{1\ mole}{6.022x10^{23}}  

b)

multiply by  1 mole15.999 g\ \frac{1\ mole}{15.999\ g}  

c)

multiply by 6.022x10231 mole\frac{6.022x10^{23}}{1\ mole}  

d)

multiply by 15.999 g1 mole\frac{15.999\ g}{1\ mole}  

10.
The molar mass of an element is the mass of one ____ of the element.
a)
atom
b)
molecule
c)
mole
d)
gram
11.
How many moles of carbon atoms are there in 5g of carbon?
a)
60 mol
b)
17 mol
c)
0.42 mol
d)
7 mol
12.
How many moles are in 4.5x1024 particles?
a)

7.47 particles

b)

7.47mol

c)
2.71x1047 mol
d)
2.71x1047 particles
13.

How many molecules are in 150.0g of Na2SO4?

a)

9.03x1025 molecules

b)

1.056 molecules

c)

6.357x1023 molecules

d)

5.701x1023 molecules

14.

Find the mass in grams of 6.022 x 10236.022\ x\ 10^{23}    molecules of diatomic fluorine gas . Round to the hundredths place (2 decimal places). Enter only the number.

(a)  

15.

Which of the following dimensional analysis setups will correctly convert 4.00x1023atoms of cobalt to moles of cobalt? How many moles of colbalt are there?

a)

setup B : 0.664 mol Co

b)

setup A: 2.41x1047mol Co

c)

setup A : 0.664 mol Co

d)

setup B: 2.41x1047mol Co

16.

Standard temperature and pressure (STP) mean

a)

A temperature of 0°C and a pressure of 101.3 kPa, or 1 atmosphere (atm).

b)

A temperature of 100°C and a pressure of 101.3 kPa, or 1 atmosphere (atm).

c)

A temperature of 0°K and a pressure of 10 atmosphere (atm).

17.

At STP, 1 mol, or representative particles, of any gas occupies a volume of......................

a)

24.4 L

b)

44.2 L

c)

22.4 L.

18.

The quantity, 22.4 L, is called the ______ of a gas.

a)

molar volume

b)

molar mass

c)

Atomic volume

19.

What is the volume of 3 moles of hydrogen gas at STP?

a)

22.4 L

b)

24 L

c)

67.2 L

d)

89.6 L

20.

Which of the following choices best describes the number of particles found in 3 moles of copper?

a)

2.408 x 1024 Particles

b)

1.806 x 1024 Particles

c)

1.204 x 1024 Particles

d)

6.02 x 1023 Particles

21.
A compound consists of 72.2% magnesium(Mg) and 27.8% nitrogen(N) by mass. What is the empirical formula?
a)
Mg4N3
b)
MgN2
c)
Mg3N2 
d)
MgN
22.
Which of the following is considered an empirical formula?
a)
CH3COOH
b)
C6H12O6
c)
H2O
23.
You are given the following percentages: 40.05% S and 59.95% O. Find the empirical formula for these elements.
a)
SO
b)
SO2
c)
SO3
d)
SO4
24.
Which pair has the same empirical formula?
a)
NaCrO4 and Na2Cr2O7
b)
C2H4O2 and C6H12O6
c)
C3H6O3 and C2H6O2
d)
CH4 and C2H6
25.
A compound consists of 72.2% magnesium(Mg) and 27.8% nitrogen(N) by mass. What is the empirical formula?
a)
Mg4N3
b)
MgN2
c)
Mg3N2 
d)
MgN
26.
A formula with the lowest whole # ratio of elements in a compound is called
a)
Molecular Formula
b)
Chemical Formula
c)
Empirical Formula 
d)
Distance Formula
27.
Glycerol has a molar mass of 92.09g/mol. Its percent composition is: 39.12% C, 8.75% H, and 51.12% O. What is the molecular formula for glycerol?
a)

C2H3O2

b)

CH2O

c)

C2H4O2

d)

C3H8O3

28.

2.40 g of an explosive, J, contains 0.473 g of nitrogen. J also contains 33.8% carbon and 1.41% hydrogen by mass. The remainder of J is oxygen.


What is the empirical formula of J?

a)

C4HNO2

b)

CH2N2O

c)

C2HNO2

d)

CHNO

29.
Given the following: 42.07% Na, 18.89% P, and 39.04% O, determine the empirical formula.
a)
 NaPO2
b)
Na2PO3
c)
Na3PO4
d)
NaPO4
30.

Which one is the empirical formula?

C4H6

a)

CH

b)

CH3

c)

C2H3

d)

C4H6

31.

Carbon monoxide, a deadly gas, has a chemical formula of CO (one carbon atom with one oxygen atom). If you look at the total atomic mass of CO, does carbon or oxygen make up more of the mass?

a)

carbon

b)

oxygen

c)

they are exactly the same

d)

it is impossible to tell

32.

What percentage of the total atomic mass of carbon monoxide (CO) is composed of oxygen?

a)

29%

b)

43%

c)

57%

d)

73%

33.

What percentage of the total atomic mass of carbon monoxide (CO) is composed of carbon?

a)

29%

b)

43%

c)

57%

d)

73%

34.

Magnesium bromide (one magnesium atom with two bromine atoms) has a chemical formula of MgBr2. If you look at the total atomic mass of MgBr2, does magnesium or bromine make up more of the mass?

a)

bromine

b)

magnesium

c)

they are exactly the same

d)

it is impossible to tell

35.

What percentage of the total atomic mass of magnesium bromide (MgBr2) is composed of magnesium?

a)

13%

b)

43%

c)

63%

d)

87%

36.

What percentage of the total atomic mass of magnesium bromide (MgBr2) is composed of bromine? Hint - consider the mass of both atoms of bromine in your calculation.

a)

13%

b)

43%

c)

63%

d)

87%

37.

Lithium phosphide (three lithium atoms with one phosphorus atom) has a chemical formula of Li3P. If you look at the total atomic mass of Li3P, does lithium or phosphorus make up more of the mass?

a)

lithium

b)

phosphorus

c)

they are exactly the same

d)

it is impossible to tell

38.

What percentage of the total atomic mass of lithium phosphide (Li3P) is composed of lithium? Hint - consider all three atoms of lithium in your calculation.

a)

13%

b)

29%

c)

40%

d)

60%

39.

What percentage of the total atomic mass of lithium phosphide (Li3P) is composed of phosphorus?

a)

13%

b)

29%

c)

40%

d)

60%

40.

What percentage of the total atomic mass of calcium nitrate (Ca(NO3)2) is composed of nitrogen? Hint - another way to think of calcium nitrate is Ca(NO3)(NO3).

a)

17%

b)

24%

c)

29%

d)

59%

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