Unit 8/9 Review (Moles, % Comp, and Empirical)

What is the empirical formula if you have 36.84% nitrogen and 63.16% oxygen?

• NO
• N₂O₃
• N₂O₄
• N₂O₅

An empirical formula:

• is a formula that calculates the coefficients of a compound in a balanced equation.
• is the simplest whole-number ratio of moles of elements in the compound.

You are given the following percentages: 40.05% S and 59.95% O. Find the empirical formula for these elements. (keep two decimal places throughout calculations)

• SO
• SO₂
• SO₃
• SO₄

Which pair has the same empirical formula?

• NaCrO₄ and Na₂Cr₂O₇
• C₂H₄O₂ and C₆H₁₂O₆
• C₃H₆O₃ and C₂H₆O₂
• CH₄ and C₂H₆

A compound came out with the following ratio
3 Carbon: 1.49 Phosphorus: 2 Oxygen- what would be the empirical formula?

• Ca₆P₃O₄
• C₃PO₂
• C₆P₃O₄
• C₃P₃O₂

20% Ca, 80 Br. Empirical Formula =

• CaBr

• CaBr₂

• Ca₂Br

• Ca₂Br₂

Tags

NGSS.HS-PS1-7

What is the percent by mass of magnesium in MgO?

• 20%
• 40%
• 50%
• 60%

What is the percent composition by mass of sulfur in the compound MgSO₄ (gram formula mass = 120 g/mol)?

• 20%
• 27%
• 46%
• 53%

What is the percent by mass of fluorine in CaF₂ (gram-formula mass = 78 g/mol)?

• 24%
• 49%
• 51%
• 65%

What is the percent composition of S in the formula (NH₄)₂S ?

• 12.05%
• 19.30%
• 47.11%
• 56.18%