Empirical and Molecular Formulas

In which compound is the percent composition by mass of Cl equal to 42%?

• HClO (gram formula mass = 52 g/mol)
• HClO₂ (gram formula mass = 68 g/mol)
• HClO₃ (gram formula mass = 84 g/mol)
• HClO₄ (gram formula mass = 100 g/mol)

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

• 20%
• 27%
• 46%
• 53%

How many molecules are in 2.5 mol of NaCl?

• 1.5 x 10²⁴ molecules

• 1.5 molecules

• 4.15 molecules

• 1.5 x 10²³ molecules

How many moles are in 19.82 g Mg?

• 1.23 mol Mg

• 481.70 mol Mg

• 1.00 mol Mg

• 0.82 mol Mg

Tags

NGSS.HS-PS1-7

How many moles are in 3.01 x 10²² atoms of magnesium?

• 0.05 moles

• 1.81 x 10⁴⁶ moles

• 5.00 x 10²¹ moles

• 5.00 moles

Tags

NGSS.HS-PS1-7

How many grams are in 1.2 x 10²⁴ atoms of C?

• 29.34 grams

• 23.94 grams

• 6.02 grams

• 1.21 grams

Tags

NGSS.HS-PS1-7

What is the percent composition by mass of sulfur (S) in the compound MgSO₄?

• 20.22%

• 19.85%

• 26.64%

• 28.64%

Calculate the number of atoms in 0.0340 g Zn.

• 5.200 x 10^-4 atoms Zn
• 3.130 x 10²³ atoms Zn
• 3.130 x 10²⁰ atoms Zn
• 1 atom Zn

Tags

NGSS.HS-PS1-7

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