You perform a combustion analysis on a 200 mg sample of a substance that contain

Question

You perform a combustion analysis on a 200 mg sample of a substance that contains C, H, and O and you find that 500 mg CO2 are produced along with 306 mg H20. If the substance contains only C, H, O, what is the empirical formula? A compound used in the manufacture of Saran is 24.7% H, and 73.2% Cl by mass. The storage of 4 g of the compound in a 700-mL vessel at 0 Degrees Celsius results in a pressure of 2.5 atm. What is the molecular formula of the compound: An expanding gas absorbs 2.0 kj of heat. If it's internal energy increases by 2.5 kj What quantity of work is involved? Estimate the change in H for the process

Explanation / Answer

4) the combustion equation for Carbon is

C(s) + O2 --> CO2(g)

so here 44grams of CO2 is produced from 12 grams of carbon

So 500mg will be produced from = 12 X 500/ 44 mg of carbon = 136.36 mg of carbon

Moles of carbon present = mass / Mol wt = 136.36 / 12 = 11.36millimoles

Similarly combustion equation for hydrogen is

H2(g) + 0.5O2(g) --> H2O(l)

so here 18 grams of water is produced from 2 grams of Hydrogen

so 306 mg of water will be produced from = 2 X306 / 18 mg of hydrogen = 34mg of hydrogen

Moles of hydrogen present = 34millimoles

so amount of oxygen = 200- (34 + 136.36) = 29.64mg

Moles of oxygen present = 29.64 / 16 = 1.85 millimoles

Emperical formula = C6H18O

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