Mole Concept & Chemical Equations

Question 1

Name 5 common anions and their charges

Answer 1

Carbonate CO₃²⁻
Nitrate NO3−
Phosphate PO₄³⁻
Sulfate SO₄²-
Chloride Cl-

Question 2

Prefixes are generally used to name compounds. Name the prefixes for 1, 2, 3, 4 and 5 respectively.

Answer 2

Mono - 1
Di - 2
Tri - 3
Tetra - 4
Pent - 5

Question 3

What does aqueous mean?

Answer 3

It means the product/reactant of the equation exists as ions in a solution, water was added.

Question 4

What are the steps to write an ionic equation for a reaction?

Answer 4

1. Write the balanced chemical equation for the reaction
2. ONLY IONIC COMPOUNDS that are in AQUEOUS state should be written as ions
3. Remove all spectator ions
4. Obtain the final ionic equation

Question 5

Formula for percentage by mass of an element present in a compound?

Answer 5

Ar × (no. of atoms)/Mr of compound × 100%

Question 6

Convert 24dm³ into cm³

Answer 6

24000cm³

Question 7

1 mole of any type of gas, regardless of their chemical formula & Mr, all have the same volume of _______.

Answer 7

24dm³ or 24000cm³

Question 8

Concentration can be measured in 2 types of units. What are the 2 units?

Answer 8

Theconcentrationof asolutioncan be shown in g/dm³or mol/dm³

Question 9

In a reaction, what is the limiting reactant and the excess reactant?

Answer 9

• The limiting reactant is the reactant that is completely used up first. It limits the amount of product that can be formed.
• The excess reactant is the reactant that would still remain in excess even when the limiting reactant has been completely reacted.

Question 10

Explain clearly what is percentage yield and provide the formula.

Answer 10

Percentage yield = (actual yield/theoretical yield) × 100%
Actual yield refers to the actual amount of product obtained.
Theoretical yield refers to the maximum amount of products formed based on chemical calculation.

Question 11

Formula for percentage purity?

Answer 11

(Mass of pure substance/mass of sample) × 100%