RPAL Excess Reagents 3

Question 1

In CH₄ + 2O₂ → CO₂ + 2H₂O, if 3 mol CH₄ and 8 mol O₂ react, how many moles of O₂ remain?

Accepted Answer

2 mol

Answer

1 mol

Answer

3 mol

Answer

0 mol

Question 2

When converting excess reagent from moles to grams, which formula is used?

Accepted Answer

Mass = moles × molar mass

Answer

Mass = moles ÷ molar mass

Answer

Mass = moles × Avogadro's number

Answer

Mass = moles + molar mass

Question 3

For the reaction 2HCl + Ca → CaCl₂ + H₂, if 4 mol HCl and 3 mol Ca are used, what is the excess reagent and how much remains?

Accepted Answer

Ca; 1 mol remains

Answer

HCl; 1 mol remains

Answer

Ca; 2 mol remain

Answer

HCl; 2 mol remain

Question 4

In an RPAL table, the 'leftover' row reports which value?

Accepted Answer

The moles of excess reagent remaining after the reaction

Answer

The moles of product that could have been formed

Answer

The initial moles of limiting reagent

Answer

The moles of all reactants combined

Question 5

Which scenario results in the largest amount of excess reagent remaining?

Accepted Answer

Starting with a large surplus of one reactant relative to the stoichiometric requirement

Answer

Using exactly stoichiometric amounts of both reactants

Answer

Starting with equal masses of both reactants

Answer

Using the minimum required amount of each reactant

Question 6

After a reaction, if 12 g of excess O₂ remains (molar mass = 32 g/mol), how many moles of excess O₂ are present?

Accepted Answer

0.375 mol

Answer

0.5 mol

Answer

384 mol

Answer

3.75 mol