14. A gas sample contains 40g of CH4 and 2.0 g of He. What is the volume of the

Question

14. A gas sample contains 40g of CH4 and 2.0 g of He. What is the volume of the sample at STP A) 130 L ) 11 L C) 17L D) 30. L E) 5.6L 15. What is the mass of a somple of 02 gas, which has a pressure of 740. mmHg, at a temperature of 25 C, in a volume of 250. ml? A) 0.318 g 8) 3.82 g C) 201 g D) 292 9 E) 320.9 16. Which of the following molecules can form hydrogen bonds? A) CH4 B) NaH C) NH3 D) BH3 E) HI 17. Which one of the following compounds will NOT be soluble in water? A) NaOH B) PbS C) K2504 D) LiNO3 E) Mgcl2 8. What is the concentration, in m/v percent, of a solution prepared from 50. g NaCl and 2.5 L of water? A) 5.0% B) 2.0% C) 0.020% D) 0,050% E) 20%

Explanation / Answer

Ans 14

Moles of CH4 = mass/molecular weight

= 4g /16g/mol

= 0.25 mol

Moles of H2 = mass/molecular weight

= 2g / 2g/mol

= 1 mol

Total Moles of gas sample = 0.25 + 1 = 1.25 mol

At STP

Pressure P = 1 atm

Temperature T = 273.15 K

From the ideal gas equation

Volume = moles x Gas constant x Temperature / pressure

= 1.25 mol x 0.0821 L-atm/mol-K x 273.15 K / 1 atm

= 28 L

Option D is the correct answer (closest)

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