RPAL Excess Reagents 2

Question 1

In N₂ + 3H₂ → 2NH₃, you start with 2 mol N₂ and 3 mol H₂. After the reaction, how many moles of excess reagent remain?

Accepted Answer

N₂; 1 mol remains

Answer

H₂; 1 mol remains

Answer

N₂; 0.5 mol remains

Answer

H₂; 3 mol remain

Question 2

What units are used when reporting the amount of excess reagent remaining?

Accepted Answer

Moles or grams (depending on the question)

Answer

Only grams

Answer

Only liters

Answer

Only molecules

Question 3

Why is it useful to calculate the amount of excess reagent remaining?

Accepted Answer

To know what leftover materials are present after the reaction

Answer

To calculate the activation energy

Answer

To determine the rate of the reaction

Answer

To find the equilibrium constant

Question 4

For 2Fe + 3Cl₂ → 2FeCl₃, if 4 mol Fe and 3 mol Cl₂ react, how many moles of excess Fe remain?

Accepted Answer

2 mol Fe

Answer

1 mol Fe

Answer

4 mol Fe

Answer

0 mol Fe

Question 5

A student reports that after a reaction, 0.5 mol of the excess reagent remains. What does this tell you about the reaction?

Accepted Answer

The reaction went to completion with the limiting reagent fully consumed

Answer

The reaction did not occur

Answer

The limiting reagent is still present

Answer

Both reactants were limiting

Question 6

If both reactants are used up completely in a reaction, what can you conclude?

Accepted Answer

They were in a perfect stoichiometric ratio with no excess

Answer

One reactant must still be limiting

Answer

The reaction did not go to completion

Answer

The product yield must be 100%