Limiting & excess

What is a limiting reagent in a chemical reaction?

• A catalyst that speeds up the reaction

• The product formed in the reaction

• The reactant that is available in excess

• The reactant that is completely used up first, stopping the reaction

Answer explanation

The reactant that is completely used up first, stopping the reaction

What is the result when 2.40 g of Mg reacts with 10.0 g of O2?

• Both react completely

• No reaction occurs

• Mg is the limiting reagent

• O2 is the limiting reagent

Answer explanation

Mg is the limiting reagent because it will be completely consumed before all the O2 reacts, resulting in excess O2.

Tags

NGSS.HS-PS1-7

What happens when the reactants are not mixed in the correct stoichiometric proportions?

• One of the reactants will be entirely consumed while another will be left over

• The reaction will not occur

• The reaction will produce more products

• All reactants will be used up completely

Answer explanation

One of the reactants will be entirely consumed while another will be left over

Tags

NGSS.HS-PS1-6

What is the role of a limiting reagent in a chemical reaction?

• It speeds up the reaction

• It acts as a catalyst

• It determines when the reaction stops

• It decreases the yield of the product

Answer explanation

The role of a limiting reagent in a chemical reaction is to determine when the reaction stops.

Tags

NGSS.HS-PS1-7

The limiting reactant

• slows the reaction down

• is used up first

• is the reactant that is left over

• controls the speed of the reaction

Answer explanation

The limiting reactant is used up first, as it determines the maximum amount of product that can be formed in a reaction.

Tags

NGSS.HS-PS1-7

When two substances react to form products, what is the reactant that is used up first called?

• explosive reactant

• true reactant

• limiting reactant

• excess reactant

Answer explanation

When two substances react to form products, the reactant that is used up first is called the limiting reactant.

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

Answer explanation

The limiting reactant is Oxygen because it is consumed first in the reaction, leaving C10H8 in excess.

Tags

NGSS.HS-PS1-7

Identify the limiting reagent when 6.00 g HCl combines with 5.00 g Mg to form MgCl₂.
 
Mg +  2HCl --> MgCl₂  +  H₂   
 

• Mg

• H2

• MgCl2

• HCl

Answer explanation

HCl is the limiting reagent because it will be completely consumed before Mg in the reaction, based on the given masses.

Tags

NGSS.HS-PS1-7

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

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