A hot-air balloon is filled with air to a volume of 4.00 3 103 m3 at 745 torr and 218C. The air in the balloon is then heated to 628C, causing the balloon to expand to a volume of 4.20 3 103 m3 . What is the ratio of the number of moles of air in the heated balloon to the original number of moles of air in the balloon

Respuesta :

Answer : The ratio of the number of moles of air in the heated balloon to the original number of moles of air in the balloon is, 0.5735

Explanation :

First we have to calculate the original number of moles of  air in the balloon.

Using ideal gas equation:

PV = nRT

or,

[tex]n_1=\frac{PV_1}{RT_1}[/tex]

where,

[tex]n_1[/tex] = original number of moles of air in the balloon = ?

P = pressure of gas = 745 torr = 99308.5 Pa     (conversion used : 1 torr = 133.3 Pa)

[tex]V_1[/tex] = volume of gas = [tex]4.00\times 10^3m^3[/tex]

[tex]T_1[/tex] = temperature of gas = [tex]218^oC=273+218=491K[/tex]

R = gas constant = [tex]8.314Pa.m^3/mol.K[/tex]

Now put all the given values in the above equation, we get:

[tex]n_1=\frac{(99308.5 Pa)\times (4.00\times 10^3m^3)}{(8.314Pa.m^3/mol.K)\times (491K)}[/tex]

[tex]n_1=97309.4mol[/tex]

Now we have to calculate the number of moles of  air in heated balloon.

Using ideal gas equation:

PV = nRT

or,

[tex]n_2=\frac{PV_2}{RT_2}[/tex]

where,

[tex]n_2[/tex] = number of moles of air in heated balloon = ?

P = pressure of gas = 745 torr = 99308.5 Pa     (conversion used : 1 torr = 133.3 Pa)

[tex]V_2[/tex] = volume of gas = [tex]4.20\times 10^3m^3[/tex]

[tex]T_2[/tex] = temperature of gas = [tex]626^oC=273+626=899K[/tex]

R = gas constant = [tex]8.314Pa.m^3/mol.K[/tex]

Now put all the given values in the above equation, we get:

[tex]n_2=\frac{(99308.5 Pa)\times (4.20\times 10^3m^3)}{(8.314Pa.m^3/mol.K)\times (899K)}[/tex]

[tex]n_2=55804.1mol[/tex]

Now we have to calculate the ratio of the number of moles of air in the heated balloon to the original number of moles of air in the balloon.

[tex]\frac{n_2}{n_1}=\frac{55804.1mol}{97309.4mol}=0.5735[/tex]

Thus, the ratio of the number of moles of air in the heated balloon to the original number of moles of air in the balloon is, 0.5735

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