Question

1 A pure hydrocarbon is used in bottled gas for cooking and heating. When 10 cm of the hydrocarbon is burned in 70 cm of oxygen (an excess), the final gaseous mixture contains 30 cm of carbon dioxide and 20 cm of unreacted oxygen. All gaseous volumes were measured under identical conditions. What is the formula of the hydrocarbon? A C₂Ho B CaHo c Cato Chio 2 On collision, airbags in cars inflate rapidly due to the production of nitrogen. The nitrogen is formed according to the following equations. 2NaN → 2Na + 3N2 10Na + 2KNO, K2O + 5NaO + N2 How many moles of nitrogen gas are produced from 1 mol of sodium azide, NaNg? A 1.5 B 1.6 C 3.2 3.2 D 4.0

Answer 1

Q1) problem is based on eudiometry, at constant pressure and temperature (P ,T = constant ) volume of gas is proportional to moles.

Let formula of hydrocarbon is C_{​​​​​​x} ​H_{​​​​​​y}

C_​​​​xHy ( g ) + ( x + y/ 4) O2( g ) $\rightarrow$xCO2 ( g ) + y/2 H2O( l )

According to question volume of CO2 = x ( 10 )= 30 cc , x = 3

Volume of O2 reacted = 50 cc = ( x + y /4 )x 10

Solving this y = 8

So formula is C3H8

Correct answer is C option

2) 2NaN3 $\rightarrow$ 2 Na + 3 N2

1 mol NaN3 form 1 mol Na and 1.5 mol N2 according to first reaction.

10 Na + 2 KNO3$\rightarrow$ K2O + 5 Na2O + N2

So from 1 mol Na will form 1/10 = 0.1 mol N2

So total moles of N2 from both reaction = 1.5 + 0.1 = 1.6 mol N2

So correct answer is b option