Moles Review

You are a new, fresh-faced chemistry student who is just okay at using a calculator. You calculate the molar mass of Ca(ClO₂)₂ to be 139.53 g/mol. What is the percent error of your calculation?

• 79.7%

• 20.3%

• 25.4%

The empirical formula of a compound is C₂H₃O. The actual compound has a molar mass of 215 g/mol. What is the molecular formula of the compound?

• C₂H₃O

• C₄H₆O₂

• C₈H₁₂O₄

• C₁₀H₁₅O₅

There are 9.4 x 10²² atoms of H in how many grams of C₂H₆?

• 0.78 g

• 4.7 g

• 0.16 g

• 0.95 g

A compound contains 16.07 g of zinc and 3.93 g of oxygen. What is the percent mass of oxygen in the compound?

• 19.7%

• 80.4%

• 24.5%

Tags

NGSS.MS-PS1-1

How many formula units are in 150 g of NaCl?

• 1.5 x 10²⁴ FUN NaCl

• 2.5 x 10²⁴ FUN NaCl

• 3.9 x 10²⁴ FUN NaCl

Tags

NGSS.HS-PS1-7

What is the mass, in grams, of 1.2 moles of lead (IV) nitrate?

• 550 g

• 320 g

• 270 g

• 810 g

What is the percent composition of fluorine in sulfur hexafluoride?

• 28.13%

• 78.04%

• 21.96%

• 54.23%

A compound contains 84.98% mercury (Hg) and 15.02% chlorine (Cl). What is the empirical formula of the compound?

• Hg₆Cl

• HgCl

• HgCl₂

• Hg₂Cl

How many fluorine ions are in 0.320 moles of AlF₃?

• 1.93 x 10²³ ions

• 5.78 x 10²³ ions

• 6.42 x 10²² ions

• 3.85 x 10²³ ions

Which of the samples shown below contains the greatest number of molecules?

• 1.66 moles of CH₄

• 5.30 x 10²⁴ molecules of CO₂

• 23.0 grams of OF₂

• 8.44 x 10²² molecules of Cl₂