Moles, Percent Composition, Empirical and Molecular Formulas

What is the percent by mass of sodium in NaCl?

• 39%
• 61%
• 35%
• 65%

Which pair has the same empirical formula?

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

A compound consists of 72.2% magnesium(Mg) and 27.8% nitrogen(N) by mass. What is the empirical formula?

• Mg₄N₃
• MgN₂
• Mg₃N₂ 
• MgN

Given the following: 42.07% Na, 18.89% P, and 39.04% O, determine the empirical formula.

•  NaPO2
• Na2PO3
• Na3PO4
• NaPO4

How many molecules of sugar (C₆H₁₂O₆) are in a mole?

• 24 molecules
• 180 molecules
• 180 g
• 6.02 x 10²³ molecules

How many grams are in 1.2 x 10²⁴ molecules of CO?

• 28 grams
• 56 grams
• 6.02 grams
• 1.2 grams

If an atom of Fluorine has an atomic mass of 19 amu, it has a Molar mass of ____

• 19 lbs.
• 19 kg
• How am I supposed to know?
• 19 g/mol

What are the units for molar mass?

• grams
• amu
• grams/mole
• liters

Tags

NGSS.HS-PS1-7

What is the mass of 0.89 mol of CaCl₂?

• 111 grams
• 0.008 grams
• 98.9 grams
• none of the choices

Avogadro’s constant is:

• 6.02 x 10²²

• 6

• 6.02 x 10²³

• 3.01 x 10²³

Tags

NGSS.HS-PS1-7