Chemistry (C5)

Chemistry revision GCSE triple science OCR gateway

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  • Created by: rafia
  • Created on: 05-03-12 09:37


What is a Mole?

A mole is the name given to a number.

One MOLE of atoms or molecules of any substance will have a mass in grams equal to the relative formula mass for that substance.

NUMBER OF MOLES= Mass(g) / Relative atomic mass

Example: How many moles in 66g of carbon dioxide?

R.A.M of C02= 12+(16x2)=44

No.of moles= Mass(g)/ R.A.M=66/44=1.5 moles

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Precipitation reactions

Precipitation reactions make insoluble salts (solids)

The solid is called a precipitate that turns or cloudy.

Precipitation reactions involve ions which have to be molten or in solution as they have to move and collide.

The two solutions form the precipitate.

An ionic equation includes all the state symbols and charges.

To test for sulfate ions

1) Add dilute HCL and barium nitrate.

2) A white precipitate will form

To test for halide ions


1) Chloride= white precipitate of lead chloride

2) Bromide= cream precipitate of lead bromide

3) Iodide=yellow precipitate of lead iodide

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