AP Stoichiometry

KNO₃ --> KNO₂ + O₂
What coefficients are needed to balance the reaction?

• 2, 2, 1
• 2, 3, 2
• 1, 2, 2
• 1, 3, 1

O₂ + CS₂ --> CO₂ + SO₂
What coefficient would go in front of the O₂?

• 1
• 2
• 3
• 4

WO₃ + H₂ --> W + H₂O
What coefficient goes in front of H₂?

• 1
• 2
• 3
• 4

 The equation for Percent Yield:

• (theoretical/experimental) X 100

• (experimental/theoretical) X 100

• (experimental - theoretical)/ theoretical X 100

Answer explanation

Subtract (theor-exp)/theor x 100 when solving for % error, not % yield

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

2H₂  +   O₂  →  2H₂O
How many moles of oxygen are consumed if 8 moles H₂ are used?

• 2
• 4
• 6
• 8

What is a Limiting Reagent?

• speeds up a reaction
• what you run out of first
• what you have left over
• slows down a reaction

What is a Excess Reagent?

• amount you end with
• what you run out of first
• what you have left over
• what you start with

For the Balanced Reaction: 3 Mg + 1 Fe₂O₃ → 3 MgO + 2 Fe; What is the Ratio of moles of Mg to moles Fe?

• 3mol Mg / 2 mol Fe
• 2 mol Mg/ 3 mol Fe
• 1 mol Fe/ 2 mol Fe
• 3 mol MgO / 2 mol Fe

If you predicted that 1.5 moles of Magnesium are used in a reaction, and you have 1.0 mole of Magnesium, how much Magnesium is in Excess?

• 0.50 moles Mg

• 1.5 moles Mg
• 1.0 mole Mg
• 0.0 Moles Mg