Amount of Substance QWatch
Stage 1A weighed sample of the mixture was treated with an excess of dilute hydrochloric acid.
The sodium chlorid*e dissolved in the acid. The magnesium oxide reacted to form a solution of magnesium chloride. The magnesium also reacted to form hydrogen gas and a solution of magnesium chloride. The hydrogen produced was collected.
When a 2.65 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 Stage 2 6.41 g
Use these results to calculate the number of moles of original magnesium oxide in 100 g of the mixture.
I am not in need of the working out, rather a sequence of steps and the reasoning behind:
A) Form equations
B) Find moles of hydrogen (=moles of Mg Stage 1)
C) Find moles of MgO (Stage 2)
If you don't mind, I have another Q I had great difficulty working out:
A student carried out an experiment to find the mass of FeSO4.7H2O in an impure sample, X.
The student recorded the mass of X. This sample was dissolved in water and made up to 250 cm3 of solution.
The student found that, after an excess of acid had been added, 25.0 cm3 of this solution reacted with 21.3 cm3 of a 0.0150 mol dm–3 solution of K2Cr2O7
(a) Use this information to calculate a value for the mass of FeSO4.7H2O in the sample of X.
Main thing I really don't understand is how you form the equation
Hope that helps
There is a change in ox state for both transition metals of the Fe2+/3+ and Cr6+/3+ and the wording and style of question looks similar to the redox q's that I have practised so I just put two n two together, that all.
Hope that helps