1 Lets show the formula for molecular speed at work Provide

1. Let\'s show the formula for molecular speed at work. Provide a line-by-line solution for the molecular speed of

each of the following five gases at 300K: CO, SF6, H2S, Cl2, HBr. You must show your work for each gas to get

full credit (6 points for each gas). Finally, use these speeds to help place the five gases in order of increasing

average molecular speed i.e. lowest to highest speeds (3 points).

Solution

ANS:

As average speed of molecules of gases are given v = S Q R T (8RT/pi x M),

Where R is gas constant, T is Temp. In Kelvin, pi = 22/7 or 3.147 and M is molar mass of the gas.

Thus average speed is inversely proportional to the square root of molar mass of the gas.
Now molar masses of CO = 28; SF6 = 146; H2S = 34; Cl2 = 71; HBr = 81
In increasing order molar masses are: CO (28) < H2 S (34) < Cl2 (71) < HBr(81) < SF6(146)
Therefore, Average speed will be in the order : CO > H2S > Cl2 > HBr > SF6