Question

mass of empty beaker-----------132.862 g

mass of beaker with unknown sample--------133.343g

ass of crucible------------41.962g

mass of crucible with BaSO4---------------42.631g

A) calculate the number of moles of BaSO4 that were collected

B) calulate the number of moles of SO4^2- ion that were in the unknown

C) calulate the mass of the sulfate ion in the unknown

D) calculate the mass percentage of the sulfate ion in the unknown sample.

Answer 1

Given data

Mass of empty beaker = 132.862 g

Mass of beaker with unknown = 133.343g

Hence mass of unknown = 0.481g.

Mass of crucible = 41.962g

Mass of crucible with BaSO4= 42.631g

Hence, mass of BaSO4 = 0.669g.

The molecular weight of BaSO4 = 233.43g

We know that,

A)Mol. Wt. of molecule = 1 mole

So, 233.43g BaSO4 = 1 mole

0.669g BaSO4 = 0.699 / 233.43 = 0.002865 = 2.865 x 10^-3 moles

The number of moles of BaSO4 that were collected are 2.865 x 10^-3.

B)Dissociation of BaSO4 gives 1 SO4^- sulphate ion, hence moles of BaSO4 and SO4^‑ are same.

Moles of SO4^- sulphate ion = Moles of BaSO4 in Unknown.                 

i.e. = mass of unknown / M.W. of BaSO4 = 0.481 / 233.43 =0.00206 = 2.06 x 10^-3.

C) M.W. of SO4^-= 32+64 =96g (S= 32, O=16)

1 mol SO4^- = 96g

So, 2.865 x 10^-3 moles of unknown = 2.865 x 10^-3 x 0.669 = 1.917 x 10^-3g.

Mass of sulphate in unknown is 1.917 x 10^-3g.

D) % mass of sulphate ion = [(mass of SO4^-)/(mass of BaSO4)]x100 = (1.917 x 10^-3/0.669) x 100 = 0.2865 %

% mass of sulphate ion in unknown sample is 0.2865 %.Given data

Mass of empty beaker = 132.862 g

Mass of beaker with unknown = 133.343g

Hence mass of unknown = 0.481g.

Mass of crucible = 41.962g

Mass of crucible with BaSO4= 42.631g

Hence, mass of BaSO4 = 0.669g.

The molecular weight of BaSO4 = 233.43g

We know that,

A)Mol. Wt. of molecule = 1 mole

So, 233.43g BaSO4 = 1 mole

0.669g BaSO4 = 0.699 / 233.43 = 0.002865 = 2.865 x 10^-3 moles

The number of moles of BaSO4 that were collected are 2.865 x 10^-3.

B)Dissociation of BaSO4 gives 1 SO4^- sulphate ion, hence moles of BaSO4 and SO4^‑ are same.

Moles of SO4^- sulphate ion = Moles of BaSO4 in Unknown.                 

i.e. = mass of unknown / M.W. of BaSO4 = 0.481 / 233.43 =0.00206 = 2.06 x 10^-3.

C) M.W. of SO4^-= 32+64 =96g (S= 32, O=16)

1 mol SO4^- = 96g

So, 2.865 x 10^-3 moles of unknown = 2.865 x 10^-3 x 0.669 = 1.917 x 10^-3g.

Mass of sulphate in unknown is 1.917 x 10^-3g.

D) % mass of sulphate ion = [(mass of SO4^-)/(mass of BaSO4)]x100 = (1.917 x 10^-3/0.669) x 100 = 0.2865 %

% mass of sulphate ion in unknown sample is 0.2865 %.