Quarter 3 Honors Chemistry Extra Credit

How many molecules are in 2.5 mol of NaCl?

• 1.50 x10²⁴ molecules

• 1.50 molecules

• 4.15 molecules

• 1.51 x10²⁴ molecules

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

• 29.34 grams

• 23.94 grams

• 6.02 grams

• 1.21 grams

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

• 20.22%

• 19.85%

• 26.64%

• 28.64%

Which pair has the same empirical formula?

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

What is the molar mass of PbSO₄

• 303.3 g/mol
• 294.7g/mol
• 163.8g/mol
• 372g/mol

Which formula is an empirical formula?

• H₂O₂

• C₂H₆O₁₂

• CaCl₂

• N₂O₈

*What is the molar mass of B₂(CO₃)₃?

• 81.6 g/mol

• 94.8 g/mol

• 38.8 g/mol

• 201.6 g/mol

*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

The empirical formula of a compound is CH₂O, and it's molecular mass is 120 grams/molecule. Calculate its molecular formula.

• C₃H₆O₃

• C₄H₈O₄

• C₂H₄O₂

• CH₂O

Chalk is mostly made of calcium carbonate, CaCO₃. If it took 48.6 g of chalk to write your name on the sidewalk, how many moles of calcium carbonate does your name contain?

• 0.486 mol

• 0.714 mol

• 1.40 mol

• 2.06 mol