Formulas and Reactions

Question 1

What does a formula tell you?

Answer 1

Tells you what something is made up of.

Question 2

What is the compound CO2 formed from?

Answer 2

A chemical reaction between carbon and oxygen.

It contains 1 carbon and 2 oxygen atoms.

Question 3

How many molecules does H2SO4 (Sulphuric acid)?

Answer 3

• 2 hydrogen atoms
• 1 sulfur atom
• 4 oxygen atoms

Question 4

When there is brackets in a formaula:

Answer 4

Example calcium hydroxide Ca(OH)2.

The little number outside the bracket applies to everything inside the the bracket.

• 1 calcium atom,
• 2 oxygen atoms and
• 2 hydrogen atoms.

Question 5

Atoms during a chemical reaction:

Answer 5

• You still have the same atoms at the end of a chemical reaction as you had at the start
• Balanced symbol equations show the atoms at the start and end.

magnesium + oxygen → magnesium oxide

2Mg + O2 → 2MgO

Becuase atoms aren’t gained or lost, the mass of reactants = the mass of the product.

If you react 6g of manesium with 4g of oxygen = 10g of magnesium oxide.