Limiting and Excess Reactants

When does a chemical reaction stop?

• When the lab is finished

• When the excess reactant is used up

• When the limiting reactant is used up

• Chemical reactions never stop

Why is it important to identify the limiting reagent?

• The limiting reagent speeds up the reaction.

• The limiting reagent controls the amount of product formed.

• If there is no limiting reagent, the reaction will not occur.

• No stoichiometry calculations can be done without a limiting reagent.

Using the diagram, determine the limiting reactant, the product formed is water.

• oxygen

• hydrogen

• none of the reactant are limiting

• both hydrogen and oxygen

Tags

NGSS.HS-PS1-7

What are the correct steps for determining the limiting reactant?

• divide each reactant by its molar mass and look for the smallest number

• balance the chemical equation and look for the smallest coefficient

• divide the moles of each reactant by its coefficient and look for the smallest number

• divide each reactant by Avogadro's number and look for the smallest number

When the limiting reactant is used up, what happens?

• the reaction speeds up

• the reaction slows down

• the reaction moves to its 2nd stage

• the reaction stops

The limiting reactant

• .
• is used up first
• is the reactant that is left over
• .

The excess reactant

• .
• is used up first
• is the reactant that is left over
• .

Identify the limiting and excess reactants in the reaction shown.

• N₂ is limiting and H₂ is excess. 

• H₂ is limiting and N₂ is excess. 

• NH₃ is both limiting and excess.

• There is no limiting reactant. 

Tags

NGSS.HS-PS1-7

When 12 moles of O₂ reacts with 1.1 mole of C₁₀H₈ what is the limiting reactant?  C₁₀H₈ + 12 O₂ --> 10 CO₂ + 4 H₂O

• Oxygen

• C₁₀H₈

• Water

• Carbon Dioxide

Use the equation 2 Al + 3 Cl₂ ---> 2 AlCl₃. If 2 moles of aluminum and 2 moles of chlorine are reacted, identify the limiting reactant.

• AlCl₃

• Cl₂

• Al

Tags

NGSS.HS-PS1-7