9. It is found that 250. mL of gas at STP has a mass of 1.00 g. What is the mola
ID: 852471 • Letter: 9
Question
9. It is found that 250. mL of gas at STP has a mass of 1.00 g. What is the molar mass? [A] 22.4 g/mol [B] 28.0 g/mol [C] 14.0 g/mol [D] 89.6 g/mol [E] none of these 10. Calculate the density of nitrogen at STP. [A] 0.312 g/L [B] 0.625 g/L [C] 1.25 g/L [D] 0.800 g/L [E] 1.60 g/L 11. What volume of H2O(g) measured at STP is produced by the combustion of 4.00 g of natural gas (CH4) according to the following equation? CH4 (g) + 2O2(g) right arrow + CO2(g) + 2H2O(g) [A] 44.8 L [B] 5.60 L [C] 33.6 L [D] 22.4 L [E] 11.2 LExplanation / Answer
A.
250 ml of gas has mass 1 g.
At STP, molar volume gas 22400 ml.
So, number of moles is 0.011 mole
0.011 is 1g means 1 mole is 90.9 g
Ans is d (based on approximation)
B.
Nitrogen atomic mass is 14.
24 g is 1 mole of gas and occupies 22400 ml.
Density = mass/volume = 1.25 g/l (ans C)
C.
Moles of CH4 = 4/molar mass = 4/16 = 0.25 mole
By euation, 1 mole produces 2 moles water
0.25 would produce 0.5 moles water or 11.2 l (ans E)
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