Measurement, Mass & Equations (AQA GCSE Chemistry): Flashcards

What is a balanced equation?

Shows how reactant particles rearrange to make products

Atoms in chemical reactions

Not lost or made, just rearranged

Law of conservation of mass

Total mass stays same in all reactions

Reactant mass vs product mass

Mass of reactants = mass of products

Relative formula mass ($M_r$)

Sum of atomic masses in a compound

Steps to calculate $M_r$

1. Look up atomic masses 2. Multiply by atom count 3. Add values

$M_r$ of HCl (H=1, Cl=35.5)

36.5

Using balanced equations to predict masses

Use equation ratios to calculate product mass from reactants

Why mass appears to decrease

A gas product escapes from the container

Example of gas that escapes

$CO_2$ bubbles away in reactions

If all products are captured

Total mass stays the same

What do equation ratios show?

How to calculate masses of reactants and products