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# Edexcel GCSE Chemistry Concentration and moles

This page covers the following topics:

1. Moles

2. Mole ratios

3. Concentration

4. Concentration and moles

Avogadro's constant: 1 mole = 6.02 x 10²³ atoms/molecules/protons. To convert from moles to atoms (or reverse) use Avogadro's constant. Moles can also be calculated by using the pyramid (mass = moles x RFM).

The mole ratio is the ratio between the amount of moles in the compounds of a reaction. The mole ratio can be used as a conversion factor between reactants nd products, and can be worked out by looking at the coefficients in front of

A solution formed when a solute dissolves in a solvent has a concentration which can be calculted by dividing the mass of dissolved dolute in g by the volume of the solution in dm³ giving the concentration in g/dm³.

You can calculate the concentration in mol/dm³ of a solution by calculating the moles and dividing by the volume of the solution.

# 1

2g of NaOH is dissolved in 2 dm³ water. What is the concentration of the solution in mol/dm³?

# 2

A solution of HCl has a concentration of 8 g/dm³ is made. What is the volume of water you'd need to dissolve 0.002 kg of HCl in?

# 3

You are making a solution of HCl has a concentration of 2 mol/dm³. What is the volume of water you'd need to dissolve 0.5 mol NaOH in?

# 4

Calculate the number of particles in 2 mol of a substance?

# 5

200 cm³ dilute HCl contains 0.25 mol dissolved hydrogen chloride. What is the concentration of the acid in mol/dm³?

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