HON Chemistry – Unit 5 Review

General Vocabulary

1.Definitions – explain what each of these words means:

  1. mole
  1. molar mass
  1. Avogadro’s number
  1. empirical formula
  1. molecular formula

Molar Mass

2.Find the molar mass of the following:

a.KNO3d. oxygen gas molecules

b.(NH4)2CO3e. Ca(NO3)2

c.Ag2CrO4f. Pb(ClO3)2

Relative Mass

3.Consider the masses of various hardware below. Complete the chart.

Type / Mass (g) / Relative mass
Washer / 1.74
Hex nut / 3.16
Anchor / 3.00
Bolt / 7.64

a. How do you find the relative mass of different objects?

b. Explain the connection between these calculations and the atomic masses in the Periodic

Table.

Conversions: Mass (g) Moles  # of Particles(atoms/molecules)

Make sure to show your work, use units & labels.

4. Complete the following conversions involving mass:

a.How many moles are in 12.0 g Fe?

b.How many moles are there in 25.0 g of chlorine molecules?

c.How many moles are there in 0.476 g of (NH4)2SO4?

d.What is the mass of 0.0280 moles NO2?

5.Complete the following conversions Using Avogadro’s number:

  1. How many atoms are there in 0.00150 moles Zn?
  1. If you had 2.50 moles of oxygen gas molecules, what would be the mass of the gas?
  1. A 4.07 g sample of Sodium iodide, NaIcontains how many molecules of NaI?
  1. What is the mass of 3.89 x 1016 molecules of NaOH?

6. How many copper atoms are there in 14.6 grams of Cu2SO4?

Empirical and Molecular Formulas

7.Determine the empirical formula of a compound that contains 4.20 g of nitrogen and 12.0 g of oxygen.

8. What is the empirical formula of a compound that is 69.6% manganese and 30.4% oxygen?

9. Determine the empirical and molecular formulas for a compound that is made up of 39.99 g of carbon and 3.36 g of hydrogen. The molecular molar mass is 78.0 g/mol.

10.A compound is composed of 7.20 g of carbon, 1.20 g of hydrogen and 9.60 g of oxygen. The molar mass of the compound is 180 g/mole. Determine the empirical and molecular formulas of this compound.

11.What is the molecular formula of each compound?
Empirical FormulaActual Molar Mass of Molecular Formula Compound

CH78 g/mole

NO292 g/mole

11b. Draw the empirical & molecular formula of the second chemical named above (NO2).

Percent Composition

12. A compound of iron and oxygen is found to contain 28.0 g of Fe and 8.0 g of O. What is the % by mass of each element in the compound?

13. What is the % by mass of oxygen in CaCO3?

Lab Data

14. In an experiment like the zinc chloride experiment, a student put a piece of nickel in hydrochloric acid. Hydrogen gas was given off, then the liquid was evaporated off. The remaining solid, nickel chloride, was massed. Use the data below to determine the empirical formula of nickel chloride.

mass of beaker204.35 g

mass of nickel and beaker before reaction214.71 g

mass of nickel chloride and beaker after reaction227.22 g

Molarity

15. What is the molarity of a solution that contains .45 moles of solute mixed into 850 mL of solvent?

16. What is the molarity of a solution that is made by mixing 42.5 grams of CuSO4 in 2.25 L of water?

17. How many grams of salt (NaCl) are needed to make 1.75 L of a 0.90 M salt water solution?

Modeling Chemistry1U5 review v2.0