anactualmess
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Stage 1
A weighed sample of the mixture was treated with an excess of dilutehydrochloric acid.
The sodium chloride dissolved in the acid. The magnesium oxide reacted to forma solution of magnesium chloride. The magnesium also reacted to form hydrogengas and a solution of magnesium chloride. The hydrogen produced was collected.
a) Write equations for the two reactions involving hydrochloric acid
Stage 2
Sodium hydroxide solution was added to the solution formed in Stage 1 untilno further precipitation of magnesium hydroxide occurred. This precipitate wasfiltered off, collected, dried and heated strongly until it had decomposedcompletely into magnesium oxide. The oxide was weighed.
(b) Write equations for the formation of magnesium hydroxide and for its decomposition into magnesium oxide.
(c) When a 6.25 g sample of the mixture of the three solids was analysed as described above, the following results were obtained.
Hydrogen obtained in Stage 1 0.0528mol
Mass of magnesium oxide obtained in Stage2 6.41 g
Use these results to calculate the number of moles of original magnesium oxide in 100 g of the mixture


a) MgO + 2HCl ---> MgCl2 +H2O and Mg + 2HCl ----->MgCl2 + H2
b) MgCl2 + NaOH ---> Mg(OH)2 +2 NaCl and Mg(OH)2 + H2O
c) Unsure how to do this? Please help (I have worked out moles of MgO obtained in stage 2 (0.16) but don't know what else to do here?
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charco
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(Original post by anactualmess)

(c) When a 6.25 g sample of the mixture of the three solids was analysed as described above, the following results were obtained.
Hydrogen obtained in Stage 1 0.0528mol
use this to find moles of hydrogen and hence moles of magnesium and hence mass of magnesium


(Original post by anactualmess)
Mass of magnesium oxide obtained in Stage2 6.41 g
Use this data to find the total moles of MgO and hence the total moles of Mg



(Original post by anactualmess)
Use these results to calculate the number of moles of original magnesium oxide in 100 g of the mixture
The moles of magnesium + moles of magnesium oxide = total moles magnesium

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