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GCSE Chemistry
`Unit 2b' written by Applequestria

Table of Contents

Table of Contents..................................................................................................................................... 1
Rates of reaction ...................................................................................................................................... 3
Different reactions happen at different rates ..................................................................................... 3
The rate of reaction depends on four factors: .................................................................................... 3
The rate of reaction can be increased by changing any one of the…

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Making salts (continued) ........................................................................................................................ 12
Making insoluble salts by precipitation reactions ............................................................................. 12
Electrolysis ............................................................................................................................................. 13
Electrolysis (continued) .......................................................................................................................... 14
Electrolysis (continued) .......................................................................................................................... 15




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Rates of reaction
Different reactions happen at different rates
A slow reaction could be the reaction between oxygen and iron (rusting).
A medium reaction could be the reaction between magnesium and hydrochloric acid.
A fast reaction would be an explosion.

The rate of reaction depends on four factors:
Temperature
Concentration…

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Rates of reaction (continued)
The rate of a reaction can be observed by measuring how quickly the reactants are used or how
quickly the products are made. It is usually easier to measure how quickly the products are made. The
rate of a reaction can be calculated by the formula:…

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Rates of reaction (continued)
Reaction between sodium thiosulphate and dilute hydrochloric acid (for temperature):
Both reactant solutions are clear and the product precipitate of yellow sulphur clouds the
solution.
Add the sodium thiosulfate into the hydrochloric acid. The reaction produces a yellow
precipitate of sulphur. Observe a mark through the…

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Rates of reaction (continued)
Reaction rates are explained by collision theory: the rate of a reaction depends on the frequency and
energy of particle collisions. The effects of temperature, concentration and surface area on the rate of
reaction can be explained by the frequency of particle collisions.

Higher temperature increases…

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Exothermic and endothermic reactions
When chemical reactions occur, energy is transferred to or from the surroundings. An exothermic
reaction is one which transfers energy to the surroundings, usually in the form of heat and usually
shown by a rise in temperature. This means that heat is given out. Examples of…

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Acids and bases
The state symbols
(s) means solid
(l) means liquid
(g) means gas
(aq) means aqueous (dissolved in water)

The pH scale
The pH scale is used to measure the acidity or alkalinity of a solution and is measured using an
indicator such as universal indicator, which is…

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Acids and bases (continued)
Acid + Metal Salt + Hydrogen Metals react with acids to produce a salt and
hydrogen.

Metals react with acids to produce salts. For example, magnesium reacts with hydrochloric acid to
produce magnesium chloride and releases hydrogen. However, copper does not react with
hydrochloric acid and…

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Acids and bases (continued)
Acid + Metal oxide Salt + Water Metal oxides react with acids to produce a salt
and water. This is a neutralisation reaction.
Acid + Metal hydroxide Salt + Water Metal hydroxides react with acids to produce a
salt and water. This is a neutralisation reaction.…

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