Mole Conversions Practice Quiz

Instructions

Complete all problems showing your work. Remember:

Always go through MOLES as your bridge!
Calculate molar mass carefully (watch those subscripts!)
Use Avogadro's number: 6.02 × 10²³
Apply proper significant figures

Section A Calculating Molar Mass

Problem 1

Calculate the mass in grams of each of the following:

a. 1 atom Pb
b. 1 atom Ag
c. 1 molecule H₂O
d. 1 molecule C₃H₈(NO₃)₃

Section B Atoms, Molecules & Avogadro's Number

Problem 2

How many atoms are contained in each of the following?

a. 11 molecules C₂H₅OH
b. 25.0 atom Ag
c. 0.0986 g Xe
d. 72.5 g CHCl₃

Problem 3

Exactly 1 mol of carbon disulfide (CS₂) contains:

a. how many carbon disulfide molecules?
b. how many carbon atoms?
c. how many sulfur atoms?
d. how many total atoms of all kinds?

Problem 4

How many atoms of oxygen are contained in each of the following?

a. 16.0 g O₂
b. 0.622 mol MgO
c. \(6.00 \times 10^{22}\) molecules C₉H₈O₄

Problem 5

If a stack of 500 sheets of paper is 4.60 cm high, what will be the height, in meters, of a stack of Avogadro's number of sheets of paper?

Section C Grams ↔ Moles Conversions

Problem 6

How many grams of sodium contain the same number of atoms as 10.0 g of potassium?

Problem 7

One atom of an unknown element is found to have a mass of 1.79 × 10⁻²³ g. What is the molar mass of this element?

Problem 8

How many molecules of sugar are in a 5-lb bag of sugar? The formula for table sugar or sucrose is C₁₂H₂₂O₁₁.

Section D Real-World Scale Problems

Problem 9

If 20. drops of water equal 1.0 mL (1.0 cm³):

a. how many drops of water are there in a cubic mile of water?
b. what would be the volume in cubic miles of a mole of drops of water?

Problem 10

A penny has a mass of about 2.5 g. If we assume the penny is pure copper (which means the penny is very old since newer pennies are a mixture of copper and zinc), how many atoms of copper does it contain?

Problem 11

If a student weighs 18 g of aluminum and needs twice as many atoms of magnesium as she has of aluminum, how many grams of Mg does she need?

Section E Multi-Step Challenge Problems

Problem 12

White phosphorus is one of several forms of phosphorus and exists as a waxy solid of P₄ molecules. How many atoms are present in 0.350 mol of P₄?

Problem 13

Given 1.00-g samples of each of the compounds O₂, H₂O, and CH₃OH:

a. which sample will contain the largest number of molecules?
b. which sample will contain the largest number of atoms?

Show proof of your answers with calculations.

Problem 14

How many grams of Fe₂S₃ will contain a total number of atoms equal to Avogadro's number?

Problem 15

How many grams of calcium must be combined with phosphorus to form the compound Ca₃P₂?

Hint: Think about the ratio of atoms in the formula.