Calculations mix

How many molecules are there in 31.8 moles of water? (H₂O has a molar mass of 18.0 g/mol, avogadros constant: 6.022 x 10²³)

• 572 g

• 1.91 x 10²⁵ molecules

• 5.28x 10-²⁵ molecules

• 1.77 g

What is the mass of 0.75 moles of (NH₄)₃PO₄?

• 0.0044 g

• 91 g

• 110 g

• 74 g

Tags

NGSS.HS-PS1-7

Calculate the % composition by mass of oxygen present in H₂SO₄.

• 16.3%
• 65.25%
• 32.6%
• 57.14%

1.7 g of NaNO₃ (Mr = 85) is dissolved in water to prepare 0.20 dm³ of solution. What is the concentration of the resulting solution in mol dm^–3?

• 0.01

• 0.1

• 0.2

• 1.0

6.0 mol of aluminium reacts with oxygen to form aluminium oxide. What is the amount of oxygen, in mol, needed for complete reaction?

4Al(s) + 3O₂(g) → 2Al₂O₃(s)

• 1.5

• 3.0

• 4.5

• 6.0

Tags

NGSS.HS-PS1-7

2 NaClO₃ (s) --> 2NaCl (s) + 3 O₂ (g)  
12.00 moles of NaClO₃ will produce how many grams of O₂?

• 256 g of O₂
• 576 g of O₂
• 288 g O₂

Tags

NGSS.HS-PS1-7

What is the empirical formula of a substance with the molecular formula C₂H₄?

• C₂H₂

• C₂H₂

• C₁H₁

• CH₂

Tags

NGSS.MS-PS1-1

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

• Mg₄N₃
• MgN₂
• Mg₃N₂ 
• MgN

Glycerol has a molar mass of 92.09g/mol. Its percent composition is: 39.12% C, 8.75% H, and 51.12% O. What is the molecular formula for glycerol?

• C₂H₃O₂
• CH₂O
• C₂H₄O₂
• C₃H₈O₃

When 12 moles of O₂ reacts with 6 moles of C₁₀H₈, what is the limiting reactant?  
1 C₁₀H₈ + 12 O₂ --> 10 CO₂ + 4 H₂O

• Oxygen
• C₁₀H₈
• Water
• Carbon Dioxide

Tags

NGSS.HS-PS1-7