C4.3 - From masses to balanced equations

Question 1

Stoichiometry of a reaction

Answer 1

Stoichiometry of a reaction is the ratio of the number of moles of each:

1. Reactant
2. Prooduct

Question 2

More often than not, what do you not use when you carry out a reaction in experiments?

Answer 2

More often than not, when you carry out a reaction in experiments, you do not use the exact amounts of reactants as predicted in the balanced equation

Question 3

More often than not, when you carry out a reaction in experiments, you do not use the exact amounts of reactants as predicted in the balanced equation.
What will one of the reactants be?

Answer 3

One of the reactants will be in excess

Question 4

More often than not, when you carry out a reaction in experiments, you do not use the exact amounts of reactants as predicted in the balanced equation.
One of the reactants will be in excess.
Example

Answer 4

For example, if you add dilute hydrochloric acid to magnesium ribbon, hydrogen gas is given off and you see bubbles rising from the magnesium

Question 5

if you add dilute hydrochloric acid to magnesium ribbon, hydrogen gas is given off and you see bubbles rising from the magnesium.
If the reaction stops (no more bubbles of gas appear), but there is still magnesium ribbon, the magnesium is in excess.
Why does the reaction stop?

Answer 5

The reaction stops because all the acid has been used up

Question 6

if you add dilute hydrochloric acid to magnesium ribbon, hydrogen gas is given off and you see bubbles rising from the magnesium.
If the reaction stops (no more bubbles of gas appear), but there is still magnesium ribbon, the magnesium is in excess.
The reaction stops because all the acid has been used up, so what is the hydrochloric acid?

Answer 6

The hydrochloric acid is called the limiting reactant

Question 7

Limiting reactant or reagent

Answer 7

Limiting reactant or reagent is the:
1. Reactant
Or,
2. Reagent
that gets used up first in a reaction

Question 8

You can work out which reactant/reagent is the limiting reactant/reagent from the balanced equation, if you know what?

Answer 8

You can work out which reactant/reagent is the limiting reactant/reagent from the balanced equation, if you know the number of moles of reactants you start with

Question 9

More often than not, when you carry out a reaction in experiments, you do not use the exact amounts of reactants as predicted in the balanced equation.
One of the reactants will be in excess.
For example, if you add dilute hydrochloric acid to magnesium ribbon, hydrogen gas is given off and you see bubbles rising from the magnesium.
If the reaction stops (no more bubbles of gas appear), but there is still magnesium ribbon, then what?

Answer 9

If the reaction stops (no more bubbles of gas appear), but there is still magnesium ribbon, the magnesium is in excess