Skip to content
MathsGenie logo
Open app

Course home

  1. IGCSE
  3. Chemistry Edexcel
  5. Question bank

Chemical formulae, equations and calculations

EasyMedium
1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768697071727374757677
Question 53

Crystals of hydrated barium chloride, BaCl2⋅xH2O\text{BaCl}_2 \cdot x\text{H}_2\text{O}BaCl2​⋅xH2​O, contain water of crystallisation.

A student heated a sample of the hydrated crystals in a crucible to remove the water of crystallisation in order to find the value of xxx. The crucible was heated, allowed to cool, and weighed again. This process was repeated until two consecutive masses were the same (heating to constant mass).

When hydrated barium chloride crystals are heated, they decompose according to the following equation:

BaCl2⋅xH2O→BaCl2+xH2O \text{BaCl}_2 \cdot x\text{H}_2\text{O} \to \text{BaCl}_2 + x\text{H}_2\text{O} BaCl2​⋅xH2​O→BaCl2​+xH2​O

The following masses were recorded:

  • Mass of empty crucible = 15.82 g
  • Mass of crucible +BaCl2⋅xH2O=20.70 g+ \text{BaCl}_2 \cdot x\text{H}_2\text{O} = 20.70 \text{ g}+BaCl2​⋅xH2​O=20.70 g
  • Mass of crucible and BaCl2\text{BaCl}_2BaCl2​ after heating to constant mass = 19.98 g
a.

Calculate the mass of BaCl2\text{BaCl}_2BaCl2​ formed after heating to constant mass.

[1]
b.

Calculate the mass of water lost from the crystals.

[1]
c.

The relative formula mass of BaCl2\text{BaCl}_2BaCl2​ is 208. The relative formula mass of water is 18. Use these values and your answers to (i) and (ii) to calculate the value of x x\,x in the formula BaCl2⋅xH2O\text{BaCl}_2 \cdot x\text{H}_2\text{O}BaCl2​⋅xH2​O.

[3]
d.

Why is it necessary to heat the crystals to constant mass?

[1]
e.

Describe a chemical test to show that the liquid lost was indeed water, including the expected observation.

[2]

Chemical formulae, equations and calculations Questions

  1. IGCSE
  2. /Chemistry
  3. /Chemical formulae, equations and calculations