# C3.2 Revision Cards

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• Created by: Isabel
• Created on: 09-03-14 10:10
How to calculate the concentration of a solution?
amount of solute (g)/volume of solution (dm3)
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What makes water hard?
Dissolved calcium or magnesium ions in water.
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Problems with hard water
Makes it hard to form a lather (you need a lot of soap to form a lather) and it forms an insoluble precipitate called scum, which makes soap easily wasted.
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Temporary and Permanent hard water
Hard water is either temporary (can be removed with boiling - the ions decompose when heated) or permanent (where the ions do not decompose when heated).
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How can temporary hard water be softened?
Boiling.
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How can permanent hard water be softened?
Using an ion exchange column. The water is passed through the column where there are little beads which have sodium ions weakly attached to them. When the water passes through, the Magnesium and Calcium ions swap places with the Sodium and the water
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(carried on)
is softened. Eventually all of the sodium ions will have been taken up, to passing a concentrated sodium chloride solution is passed through and flushes all of the mg and ca out so it can be reused.
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How else to measure concentration?
Evaporate the solution and so the solute will be left. By measuring the mass of the solute, we can find the concentration.
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How can the amount of a substance be measured?
Grams, number of particles and number of moles of particles.
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Moles equations?
number of moles = mass of element in g/relative atomic mass, number of moles of a compound = mass of compound in g/relative formula mass
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Concentration in mol dm-3?
number of moles of solute/volume of solution in dm3
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If soluble salts are prepared from an acid and and insoluble reactant?
The excess of the reactant can be added to ensure that all acid is used up. The excess of the reactant can be removed by filtration. The remaining solution is only salt and water. To separate the water and salt, heat the solution up.
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If soluble salts are prepared from an acid and a soluble reactant?
Titration must be used to determine the exact amount of soluble reactant that reacts with an acid. The acid and the soluble reactant can then be mixed in correct proportions. Remaining is salt and water.
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Neutralisation reaction where hydrogen ions react with hydroxide ions?
When an acid dissolves in water it forms hydrogen ions (HCl --> H+ + Cl-), when a soluble base dissolves in water it forms hydroxide ions (NaOH --> Na+ + OH-)
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Carried on
If solutions of an acid and a base are mixed together then the hydrogen and hydroxide ions combine to form water molecules. This occurs in neutralisation reactions (H+ + OH- --> H20)
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Titration calculations
(concentrations) look up past paper questions
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## Other cards in this set

### Card 2

#### Front

What makes water hard?

#### Back

Dissolved calcium or magnesium ions in water.

### Card 3

#### Front

Problems with hard water

### Card 4

#### Front

Temporary and Permanent hard water

### Card 5

#### Front

How can temporary hard water be softened?

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