Chemistry worksheet
Topic: Formula Mass And Gram Formula Mass
##### Formula Mass And Gram Formula Mass
1

Which term represents the sum of the atomic masses of the atoms in a molecule?

(1) atomic number

(2) mass number

(3) formula mass

(4) percent composition by mass

2

What is the gram-formula mass of Ca(OH)2?

(1) 29 g/mol

(2) 54 g/mol

(3) 57 g/mol

(4) 74 g/mol

3

The formula mass of a compound is the

(1) sum of the atomic masses of its atoms

(2) sum of the atomic numbers of its atoms

(3) product of the atomic masses of its atoms

(4) product of the atomic numbers of its atoms

4

Which quantity is equal to one mole of Au?

(1) the atomic mass in grams

(2) the atomic number in grams

(3) the mass of neutrons in grams

(4) the number of neutrons in grams

A hydrate is a compound that has water molecules within its crystal structure. Magnesium sulfate heptahydrate, MgSO4•7H2O, is a hydrated form of magnesium sulfate. The hydrated compound has 7 moles of H2O for each mole of MgSO4. When 5.06 grams of MgSO4•7H2O are heated to at least 300.°C in a crucible by using a laboratory burner, the water molecules are released. The sample was heated repeatedly, until the remaining MgSO4 had a constant mass of 2.47 grams. During this laboratory activity, appropriate safety equipment was used and safety procedures were followed.

5

Determine the gram-formula mass of the magnesium sulfate heptahydrate.

Allow 1 credit for 246 g/mol, or any value from 245.989 g/mol to 247 g/mol, inclusive.

The atomic mass and natural abundance of the naturally occuring isotopes of hydrogen are shown in the table below.

The isotope H-2, also called deuterium, is usually represented by the symbol “D.” Heavy water forms when deuterium reacts with oxygen, producing molecules of D2O.

6

Determine the formula mass of heavy water, D2O.

Allow 1 credit for 20. u or for any value from 19.999 u to 20.03 u, inclusive.

The table below contains selected information about chlorine and two compounds containing chlorine. One piece of information is missing for each of the substances in the table.

7

Determine the molar mass for calcium chloride.

Allow 1 credit for 111 g/mol or any value from 110. g/mol to 111.1 g/mol, inclusive.

Fruit growers in Florida protect oranges when the temperature is near freezing by spraying water on them. It is the freezing of the water that protects the oranges from frost damage. When H2O(ℓ) at 0°C changes to H2O(s) at 0°C, heat energy is released. This energy helps to prevent the temperature inside the orange from dropping below freezing, which could damage the fruit. After harvesting, oranges can be exposed to ethene gas, C2H4, to improve their color.

8

Determine the gram-formula mass of ethene.

Allow 1 credit for any value from 28 g/mol to 28.1 g/mol, inclusive.

The unique odors and flavors of many fruits are primarily due to small quantities of a certain class of organic compounds. The equation below represents the production of one of these compounds.

9

Show a numerical setup for calculating the gram-formula mass for reactant 1.

Allow 1 credit. Acceptable responses include, but are not limited to:

• 2(12.011 g/mol) + 15.9994 g/mol + 6(1.00794 g/mol)

• 2(12) + 16 + 6(1)

• 24.0 + 16.0 + 6.0

In a laboratory investigation, a solution that contains 13.2 grams of Pb(NO3)2 reacts completely with a solution that contains 12.0 grams of NaI, producing 18.4 grams of PbI2 and an undetermined mass of a second product, NaNO3. This reaction is represented by the balanced equation below.

Pb(NO3)2 + 2NaI → PbI2 + 2NaNO3

10

Determine the mass of NaNO3 produced.

Allow 1 credit for 6.8 g. Significant figures do not need to be shown.

The two naturally occurring isotopes of antimony are Sb-121 and Sb-123. The table below shows the atomic mass and percent natural abundance for these isotopes.

Antimony and sulfur are both found in the mineral stibnite, Sb2S3. To obtain antimony, stibnite is roasted (heated in air), producing oxides of antimony and sulfur. The unbalanced equation below represents one of the reactions that occurs during the roasting.

Sb2S3(s) + O2(g) → Sb2O3(s) + SO2(g)

11

Determine the percent composition by mass of antimony in stibnite (gram-formula mass = 340. g/mol).

Allow 1 credit for 71.6% or any value from 71.55% to 72%, inclusive.

12

Given the formula for heptanal:

Determine the gram-formula mass of heptanal.

Allow 1 credit for 114 g/mol. Significant figures do not need to be shown.

In 1828, Friedrich Wöhler produced urea when he heated a solution of ammonium cyanate. This reaction is represented by the balanced equation below.

13

Determine the gram-formula mass of the product.

Allow 1 credit for 60. g/mol. Significant figures do not need to be shown.

The balanced equation below represents the reaction of glucose, C6H12O6, with oxygen at 298 K and 101.3 kPa.

C6H12O6(s) + 6O2(g) → 6CO2(g) + 6H2O(ℓ)

14

Determine the mass of CO2 produced when 9.0 grams of glucose completely reacts with 9.6 grams of oxygen to produce 5.4 grams of water.

Allow 1 credit for 13.2 g or for any value from 13.155 g to 13.2042 g, inclusive.