Calcium sulphate in hard water remains dissociated in calcium ions and sulphate ions. Calculate the number of ions present in water , excluding ions of water , when 68 g of calcium sulphate is dissolved in water. (12.044×10^23)
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Calcium sulfate has an aqueous solubility of 0.21
g
per 100
mL
of water at 20
degrees
Celsius.
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Avagadro's law states that 1 mole of any substance has 6.022×10²³ molecules or atoms. That is 6.022×10²³ mol⁻¹
Find the mole of 68 g of calcium sulphate (CaSO4)
moles = mass / molar mass
molar mass of CaSO4 is 136
mole = 68/136
= 0.5 moles
Therefore the number of molecules in CaSO4 is:
0.5 moles × 6.022×10²³ mol⁻¹ = 3.0115 × 10²³
Therefore there are 3.0115 ×10²³ molecules of CaSO4 in the solution.
When 1 molecule of CaSO4 ions dissociate, 2 ions of Ca ions and SO4 ions are formed.
That means 3.0115 ×10²³ molecules will form
= 3.0115 ×10²³ molecules x 2
= 6.023 ×10²³ ions in the solution.
Find the mole of 68 g of calcium sulphate (CaSO4)
moles = mass / molar mass
molar mass of CaSO4 is 136
mole = 68/136
= 0.5 moles
Therefore the number of molecules in CaSO4 is:
0.5 moles × 6.022×10²³ mol⁻¹ = 3.0115 × 10²³
Therefore there are 3.0115 ×10²³ molecules of CaSO4 in the solution.
When 1 molecule of CaSO4 ions dissociate, 2 ions of Ca ions and SO4 ions are formed.
That means 3.0115 ×10²³ molecules will form
= 3.0115 ×10²³ molecules x 2
= 6.023 ×10²³ ions in the solution.
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