Unit 3: Stoichiometry

In the equation 2 Al₂O₃ --> 4 Al + 3 O₂, what is the mole ratio of aluminum to oxygen (aluminum is asked for, oxygen is given)?

• 10/6

• 3/4

• 4/3

• 2/3

In the reaction 2 H₂ + O₂ → 2 H₂O what is the mole ratio of oxygen to water

• 1/2

• 2/1

• 3/4

• 4/3

N₂ +  3H₂ → 2NH₃ 
How many moles of hydrogen are needed to react with 2 moles of nitrogen?

• 6
• 2
• 3
• 1

2H₂   +   O₂  →  2H₂O
How many moles of water can be produced if 8 moles H₂ are used?

• 4 moles
• 8 moles
• 16 moles
• 2 moles

2NaClO₃ (s) → 2NaCl (s) + 3O₂ (g)

12.00 moles of NaClO₃ will produce how many grams of O₂?

NaClO₃ = 106.44 g/mol ; O₂ = 32.00 g/mol

• 256 g of O₂

• 576 g of O₂

• 288 g of O₂

• 384 g of O₂

Cl₂ + 2KBr → Br₂ + 2KCl

How many grams of potassium chloride (KCl) can be produced from 356 g of potassium bromide (KBr)?

KCl = 74.55 g/mol ; KBr = 119.00 g/mol

• 749 g

• 223 g

• 479 g

• 814 g

From the reaction: B₂H₆ + 3O₂ -->2 HBO₂ + 2 H₂O

What mass of O₂ will be needed to burn 36.1 g of B₂H₆?

B₂H₆ = 27.68 g/mol

• 13.8 g O₂

• 3.91 mol of O₂

• 125 g O₂

• 41.7 g O₂

18.26 mL of a 1.50 mol/L hydrochloric acid reacts with magnesium hydroxide. Calculate the mass of magnesium hydroxide needed for the reaction.

Mg(OH)₂ + 2 HCl -> 2 H₂O + MgCl₂

Mg(OH)₂ = 58.33 g/mol ; HCl = 36.46 g/mol

• 4.68 g Mg(OH)₂

• 0.799 g Mg(OH)₂

• 0.0274 Mg(OH)₂

• 1.60 g Mg(OH)₂

Balance the following reaction :
 
CaC₂(s)   +   H₂O(l)   -->   C₂H₂(g)   +   Ca(OH)₂(aq)

• 1,2,2,2
• 1,2,1,1
• 2,1,1,1
• 2,1,2,1

What is a limiting reactant?

• the reactant that determines how much product can be made
• the reactant that is in excess
• the product that you can make the most of
• the amount of reactants that react with each other