18. Which gas will have the highest density at STP? a. Ar b. Ne c. N2 d. O2 19.

Question

18. Which gas will have the highest density at STP?
a. Ar b. Ne c. N2 d. O2

19. What maximum volume of H2 gas could be formed at STP in the reaction below, using 4.23 g of Al?
2 NaOH(s) + 2 Al(s) + 6 H2O(l) 2 NaAl(OH)4(s) + 3 H2(g)
a. 2.39 L b. 3.59 L c. 5.38 L d. 5.87 L

20. A 10.0-L flask containing an unknown amount of He, 2.00 mole of Ar, and 3.00 mole of Ne has a
total pressure of 24.5 atm at 25°C. How many moles of He are in the flask?
a. 5.00 mol b. 10.0 mol c. 114 mol d. 119 mol

21. A 10.0-L flask containing 1.00 mole of He, 2.00 mole of Ar, and 3.00 mole of Ne has a total
pressure of 24.5 atm at 25°C. What is the partial pressure of Ne in the flask?
a. 4.08 atm b. 8.17 atm c. 12.3 atm d. 24.5 atm

22. What is the root-mean-square (average) speed of a neon atom at 27°C?
a. 5.78 m/s b. 19.3 m/s c. 183 m/s d. 609 m/s

23. Which one of the following gases will have the highest rate of diffusion?
a. Argon b. Neon c. Krypton d. Xenon

24. Which property of an individual molecule is assumed to be zero in the kinetic-molecular theory?
a. Mass b. Volume c. Speed d. Kinetic Energy

Explanation / Answer

18. Argon has the highest density at STP

19.

2 moles of Al gives 3 moles of H2

Moles of Al = mass/ molar mass of aluminum = 4.23/37 = 0.157

0.157 mole of Al will give = (3/2) * 0.157 = 0.235 moles H2

1 mole = 22.4 L

0.235 mole = 0.235 * 22.4 = 5.38 L

23.

Smaller element will diffuse faster

Hence rate of diffusion will increase with decrease in size. Hence Neon will have highest rate of diffusion.

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