Question

Epsom salts is a hydrated ionic compound with the following formula: MgSO4⋅xH2O A sample of Epsom salts with a mass of 4.93 g was heated to drive off the water of hydration. The mass of the sample after complete dehydration was 2.41 g.

What is the mass of the water lost during heating?

how many moles of water were lost during heating?

What is the mass of MgSO₄ remaining in the crucible after heating?

How many moles of MgSO₄ are in the crucible after heating?

Answer 1

1)

mass of H2O = mass of hydrated salt - mass of anhydrous salt

mass of H2O = 4.93 g - 2.41 g

mass of H2O = 2.52 g

Answer: 2.52 g

2)

Molar mass of H2O,

MM = 2*MM(H) + 1*MM(O)

= 2*1.008 + 1*16.0

= 18.016 g/mol

mass(H2O)= 2.52 g

we have below equation to be used:

number of mol of H2O,

n = mass of H2O/molar mass of H2O

=(2.52 g)/(18.016 g/mol)

= 0.1399 mol

Answer: 0.1399 mol

3)

mass of MgSO4 remaining = 2.41 g

Answer: 2.41 g

4)

Molar mass of MgSO4,

MM = 1*MM(Mg) + 1*MM(S) + 4*MM(O)

= 1*24.31 + 1*32.07 + 4*16.0

= 120.38 g/mol

mass(MgSO4)= 2.41 g

we have below equation to be used:

number of mol of MgSO4,

n = mass of MgSO4/molar mass of MgSO4

=(2.41 g)/(120.38 g/mol)

= 2.00*10^-2 mol

Answer: 2.00*10^-2 mol