UNIT 3 – WORKSHEET 1: MOLE PROBLEMS



MOLE WORKSHEET NAME:

DATE:

1. Determine the mass of

a. 2.50 moles of aluminum hydroxide _____________________

b. 0.0125 moles of dinitrogen pentoxide ______________________

c. 3.12 x 1021 formula units of iron (III) sulfide ______________________

d. 4.30 x 1027 molecules of carbon monoxide gas ______________________

2. Find the number of moles in:

a. 1.25 grams of strontium nitrate ______________________

b. 0.570 g of chlorine gas (Cl2) ______________________

3. How many formula units are in 225 g of lithium oxide? ______________________

4. How many molecules are in 15.0 g of silicon tetrafluoride? ______________________

** How many atoms of fluorine are in 15.0 g of silicon tetrafluoride? ______________________

5. Find the percent composition (by mass) of nickel (II) hydroxide.

% Ni = _____

% O = _____

% H = _____

a. Use your answer to #5 to the determine the mass of nickel in 45.0 g of nickel (II) hydroxide.

_______________

b. Use your answer to #5 to determine the mass of nickel (II) hydroxide that contains 10.0 g of nickel.

_______________

6. Find the percent composition (by mass) of nitric acid.

% N = _____

% O = _____

% H = _____

a. What mass of nitric acid contains 12.0 g of nitrogen?

_______________

7. Find the molecular formula of a compound if its empirical formula is CH2O and its molar mass is 90 g/mol.

________________

MOLE WORKSHEET NAME:

DATE:

1. Determine the mass of

a. 2.50 moles of aluminum hydroxide _____________________

Al(OH)3 = 27 + (3 x 16) + (3 x 1) = 78 g/mol

2.50mol x 78 g = 195 g

1 mol

b. 0.0125 moles of dinitrogen pentoxide ______________________

N2O5 = (2 x 14) + (5 x 16) = 108 g/mol

0.0125mol x 108 g = 1.35 g

1 mol

c. 3.12 x 1021 formula units of iron (III) sulfide ______________________

Fe2S3 = (2 x 55.8) + (3 x 32.1) = 207.9 g/mol

3.12 x 1021 fu x 1 mol x 207.9 g = 1.08 g

6.02 x 1023 fu 1 mol

d. 4.30 x 1027 molecules of carbon monoxide gas ______________________

CO = 12 + 16 = 28 g/mol

4.30 x 1027 molecules x 1 mol x 28 g = 200,000 g

6.02 x 1023 molecules 1 mol

2. Find the number of moles in:

a. 1.25 grams of strontium nitrate ______________________

Sr(NO3)2 = 87.6 + (2 x 14) + (6 x 16) = 211.6 g/mol

1.25 g x 1 mol = 0.00591 mol

211.6 g

b. 0.570 g of chlorine gas (Cl2) ______________________

Cl2 = 2 x 35.5 = 71.0 g/mol

0.57 g x 1 mol = 0.00803 mol

71 g

3. How many formula units are in 225 g of lithium oxide? ______________________

Li2O = (2 x 6.9) + 16 = 29.8 g/mol

225 g x 1 mol x 6.02 x 1023 fu = 4.55 x 1024 fu

29.8 g 1 mol

4. How many molecules are in 15.0 g of silicon tetrafluoride? ______________________

SiF4 = 28.1 + (4 x 19) = 104.1 g/mol

15.0 g x 1 mol x 6.02 x 1023 molecules = 8.67 x 1022 molecules

104.1 g 1 mol

** How many atoms of fluorine are in 15.0 g of silicon tetrafluoride? ______________________

4 F atoms per molecule of SiF4, therefore 4 x 8.67 x 1022 = 3.47 x 1023

5. Find the percent composition (by mass) of nickel (II) hydroxide.

% Ni = _____

Ni(OH)2 = 58.7 + (2 x 16) + (2 x 1) = 92.7 g/mol

% Ni = 58.7/92.7 x 100% = 63.3% % O = _____

% O = 32/92.7 x 100% = 34.5%

% H = 2/92.7 x 100% = 2.2% % H = _____

a. Use your answer to #5 to the determine the mass of nickel in 45.0 g of nickel (II) hydroxide.

45.0 g x (63.3/100) = 28.5 g

_______________

b. Use your answer to #5 to determine the mass of nickel (II) hydroxide that contains 10.0 g of nickel.

10/X = 63.3/100, so X = (100 x 10)/63.3 = 15.8 g

_______________

6. Find the percent composition (by mass) of nitric acid.

% N = _____

HNO3 = 1 + 14 + (3x16) = 63 g/mol

% H = 1/63 x 100% = 1.6 % % O = _____

% N = 14/63 x 100% = 22.2%

% O = 48/63 x 100% = 76.2% % H = _____

a. What mass of nitric acid contains 12.0 g of nitrogen?

12/X = 14/63, so X = (12 x 63)/14 = 54 g

_______________

7. Find the molecular formula of a compound if its empirical formula is CH2O and its molar mass is 90 g/mol.

CH2O = 12 + (2 x 1) + 16 = 30 g/mol

90/30 = 3, so empirical formula x 3 + molecular formula =m so MF = C3H6O3

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