Question

please answer the following questions by typing, thanks.

1. How different is the measured volume from the volume if it had been obtained under STP conditions? Is the difference greater than an assumed measurement error of 5%? If not, why should we go to all this trouble to make this calculation?

2. All gases should have the same standard volume of 22.4141 L. If your value is different, then comment on the sources of error in the experiment.

3. What is the volume occupied by 11 moles of oxygen gas at STP?

4. What is the mass in grams of 10.0 L of methane (CH4) gas at STP?

Answer 1

Ans. 1. Difference in volume = Theoretical value – experimental (observed value)

            % difference in volume =

[ (Theoretical value – experimental value) / Theoretical value ] x 100

Note: The theoretical and experimental value is obtained from your experiment. From the available data, it’s not possible to get the values.

Ans. 2. Sources of errors in the experiment:

            Using, ideal gas equation, pV = nRT

Instrumental or human errors yielding erroneous values of one or more measurements (p, n, T) increases difference between thermotical and experimental value volume.   

Ans. 3. 1 mol has volume of 22.4 L at STP

So, volume occupied by 11 moles = 11 x 22.4141 L

                                                = 246.5551 L

Ans.4. Using pV = nRT

            Given,

                        V = (nRT/ p) = 22.4141 L at STP ; where, n = 1= number of moles of gas, at STP

Suppose the number of moles in 10 L = Yn or Y moles

Now,

            10 L = (Yn. RT/ p) = Y x (nRT/ p) = Y x 22.4141 L

Or, Y = 10 L / 22.4141 L = 0.4461

Thus, number of moles in 10 L methane = 0.4461

Mass of methane = number of moles x molecular mass

                                    = 0.4461 moles x 16.043 g mol^-1

                                    = 7.16 g