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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