1. When 30cm of an organic compound R of formula C, H3,0 was burnt in pure and excess oxygen and cooled to room temperature, 240cm of the residual gas was formed.
On addition of concentrated potassium hydroxide solution, the volume reduced to
180cm?
(a) (i) write the equation for the combustion of R
(ii) Determine the molecular formula of R

yes

explanation:

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1. for the first question, we must find the mass of the anhydrous salt, mgso₄. the molar mass for mgso₄·7h₂o is 246.47 g/mol, while that of mgso₄ is 120.37 g/mol.7.834 g mgso₄·7h₂o * 1 mol mgso₄·7h₂o/246.47 g * 1 mol mgso₄/1 mol mgso₄·7h₂o * 20.37 g mgso₄/mol = 0.647 g mgso₄

2. mass of water = mass of sample - mass of anhydrous salemass of water = 7.834 - 0.647 = 7.19 gpercent water in hydrate = 7.19/7.834 * 100 = 91.74%

the answer to this question is 3.