States of Matter
Q3. Using the equation of the state pV=nRT, show that at a given temperature, density of a gas is proportional to the gas pressure p.Ans. According to Ideal Gas Equation pV=nRT
and as we know n = w/M
pV= wRT/ Mp= wRTM/V
and we know density ρ = mass / volume
ρ = w/V
p= DM/RT
and as we know n = w/M
pV= wRT/ Mp= wRTM/V
and we know density ρ = mass / volume
ρ = w/V
p= DM/RT
Q6. The drain cleaner, Drainex contains small bits of aluminum which react with caustic soda to produce dihydrogen. What volume of dihydrogen at 20 °C and one bar will be released when 0.15g of aluminum reacts?Ans. The reaction can be written as:-2Al (s) + 2NaOH (aq) +2H2O (l) ⟶2NaAlO2(aq) + 3H2(g) Here, 2 moles of Al gives 3 moles of H2 gas. Moles of Aluminum = 0.15 g/ 27 =5.56×10-3 moles
∴ Moles of H2 produced= 3 /2 ×5.56×10-3 =8.33×10-3 moles
∴ Volume of H2 = P/nRT = 8.33 x 10-3 x 0.0831 x 293/ 1 = 0.203 litres∴ Volume of dihydrogen released is 0.203 litres
∴ Moles of H2 produced= 3 /2 ×5.56×10-3 =8.33×10-3 moles
∴ Volume of H2 = P/nRT = 8.33 x 10-3 x 0.0831 x 293/ 1 = 0.203 litres∴ Volume of dihydrogen released is 0.203 litres
Q13 Calculate the total number of electrons present in 1.4 g of dinitrogen gas.Ans. 1.4 g of nitrogen corresponds to 1.4/28 = 0.05 moles
0.05 moles of nitrogen corresponds to 0.05x6.022x1023 = 3.011x1022 molecules
One molecule of nitrogen contains 14 electrons
Therefore, 1.4g of nitrogen will contain 3.011x1022x14= 4.2154x1023 electrons.
0.05 moles of nitrogen corresponds to 0.05x6.022x1023 = 3.011x1022 molecules
One molecule of nitrogen contains 14 electrons
Therefore, 1.4g of nitrogen will contain 3.011x1022x14= 4.2154x1023 electrons.
Q 14 How much time would it take to distribute one Avogadro number of wheat grains, if 1010 grains are distributed each second ?Ans.Avogadro no. is 6.022x1023.The time required to distribute 6.022x1023 is 6.022x1023/1x1010 sec= 6.022 x 1013Convert unit of time from seconds to years6.022 x 1013/3600x24x365 = 1.9099x106 years
