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Acids, alkalis and titrations

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Question 26
a.

A student made a solution of lithium hydroxide by dissolving 12.0 g12.0\text{ g}12.0 g of solid lithium hydroxide in distilled water to make 500 cm3500\text{ cm}^3500 cm3 of solution.

Calculate the amount, in moles, of LiOH\text{LiOH}LiOH in 12.0 g12.0\text{ g}12.0 g of lithium hydroxide. (Relative atomic masses: Li=7\text{Li} = 7Li=7, O=16\text{O} = 16O=16, H=1\text{H} = 1H=1)

[2]
b.

Calculate the concentration, in mol/dm3\text{mol/dm}^3mol/dm3, of this solution of lithium hydroxide.

[2]
c.

The student uses the lithium hydroxide solution to find the concentration of a solution of hydrochloric acid. He uses this method:

  • use a pipette to put 25.0 cm325.0\text{ cm}^325.0 cm3 of the lithium hydroxide solution into a conical flask
  • add a few drops of phenolphthalein indicator to the solution
  • gradually add the hydrochloric acid from a burette until the solution in the flask just changes colour

The diagram shows his burette readings.

Burette readings

Complete the table, giving all values to the nearest 0.05 cm30.05\text{ cm}^30.05 cm3.

Measured ParameterVolume (cm3\text{cm}^3cm3)
burette reading at end in cm3\text{cm}^3cm3
burette reading at start in cm3\text{cm}^3cm3
volume of acid added in cm3\text{cm}^3cm3
[3]
d.

State the colour of the phenolphthalein at the start and at the end of the experiment.

[2]
e.

Why is a burette used instead of a pipette for adding the acid?

[1]
f.

Lithium hydroxide reacts with carbon dioxide.

The equation for this reaction is

2LiOH+CO2→Li2CO3+H2O 2\text{LiOH} + \text{CO}_2 \rightarrow \text{Li}_2\text{CO}_3 + \text{H}_2\text{O} 2LiOH+CO2​→Li2​CO3​+H2​O

A solution of lithium hydroxide of concentration 1.50 mol/dm31.50\text{ mol/dm}^31.50 mol/dm3 is used.

Calculate the amount, in moles, of lithium hydroxide in 400 cm3400\text{ cm}^3400 cm3 of this solution.

[1]
g.

Deduce the maximum mass, in grams, of carbon dioxide that can react with this solution of lithium hydroxide. (Relative formula mass: CO2=44\text{CO}_2 = 44CO2​=44)

[2]

Acids, alkalis and titrations Questions

  1. IGCSE
  2. /Chemistry
  3. /Acids, alkalis and titrations