 QUESTION

# mole concept

A packet of washing soda crystals have formed a white powder represented by the formula (Na(2)Co(3).xH(2)O) . the value of x may be found by dissolving a known quantity of the powder in water and titrating the solution with acid of known concentration. in an experiment a student weighed out 1.59g of the powder and dissolved it in water. the volume of the solution was made up to 250cubic-centimetres. 25.0cubic-centimetres of this solution was titrated with hydrochloric acid of concentration 0.1mol/cubic-decimetres . 25.6cubic-centimetres of the acid was required for complete reaction. the equation for the reaction is:

NA(2)CO(3) + 2HCL GIVES OUT 2NACL + H(2)O + CO(2)

a)calculate the number of moles of hydrochloric acid in 25.6cubic-centimetres of 0.1mol/cubic-decimetres

b)calculate the number of moles of sodium carbonate in 25.0cubic-centimetres sample of solution which reacted with the hydrochloric acid

c)how many moles of sodium carbonate were in 250cubic-centimetres of solution?

d)calculate the mass of sodium carbonate in the 250cubic-centimetres of solution (Ar:C=12,O=16,Na=23)

e)using your answer to part (d) , what mass of water was in the original powder?

f)how many moles of water were present in the original powder? (Ar:O=16.H=1)

g)using your answer to part (c) and (f), calculate the value of x

h)write a complete formula of the white powder showing the value of x

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