4.3.1 Quantitative chemistry (might need) PAPER 1

Question 1

How to work out %mass of an element in a compound

Answer 1

Percentage mass of an element in a compound = Ar x number of atoms in that element/Mr of the compound = ans x 100

Question 2

What is conservation of mass

Answer 2

no atoms are lost or made during a chemical reaction so the mass of the products equals the mass of the reactants.

Question 3

What does it mean if the mass increases in a reaction

Answer 3

One or more of the reactants is a gas thats found in air
The particles in a gas move around and fill the space theyre in so before the reaction they aren’t contained in the reaction vessel
When the gas reacts to form part of the product the particles become contained in the reaction vessel

Question 4

What does it mean if the mass decreased after a reaction

Answer 4

If the vessel isnt enclosed then the gas thats produced can escape