Determine Delta G degree for the following reaction: CH_4(g) + 2O_2 (g) CO_2 (g)

Question

Determine Delta G degree for the following reaction: CH_4(g) + 2O_2 (g) CO_2 (g) + 2H_2 O(l) 581.1 kJ -919.9 kJ -818.5 kJ -682 5 kJ 131.1 kJ The standard molar free energies of formation of NO_2(g) and N_2 O_4 (g) at 25 degree C are 51.840 and 98.061 kJ/mol, respectively. What is the value of K_p (in atm) for the reaction written as follows at 25 degree C? 2NO_2 N_2 O_4 5.50 times 10^11 1.00 9.66 .33 Times 10^-36 7.91 Times 10^-9 Polyethylene is a synthetic polymer or plastic with many uses 1.41 g of a polyethylene sample was dissolved in enough benzene to make 100 mL c and the osmotic pressure was found to be 1 86 torr at 25 degree C. What is the approximate molar mass of the polyethylene? 185 g/mol 118 Times 10^4g/mol 7.09 Times 10^3g/mol 1.29 Times 10^5 g/mol 1.41 Times 10^5 g/mol

Explanation / Answer

Question 14

G for the reaction is calculated by the formula:

Grxn = G0f products - G0f reactants

According to the reaction:

Grxn = G0f CO2 + 2G0f H2O - G0f CH4 - 2G0f O2

Using the values they provide:

Grxn = -394.4 kJ/mol +2(-237.4kJ/mol)-(-50.8kJ/mol)

Grxn = -818.5kJ/mol

Question 15

For this reaction we also need to calculate Grxn first using the same formula as before:

Grxn = G0f products - G0f reactants

According to the reaction:

Grxn = G0f N2O4 - 2G0f NO2

Grxn = 98.061 kJ/mol -2(51.840kJ/mol)

Grxn = -5.619kJ/mol

Now we use the equation:

Grxn = -RTlnkeq

Where R = 8.314 J/molK and T = 298K. We need to use Grxn in J/mol as well: Let's solve for keq:

keq = e-Grxn/RT

keq = e-(-5619J/mol)/((8.314J/molK)*(298K))

keq = 9.66

Question 16

We use the osmotic pressure formula:

= CRT

Where   = osmotic pressure (torr), C = concentration, R = 62,3636 torrL/molK and T = 298K

C = mol/L = grams/MM*L

Then:

= (grams*R*T/MM*L)

Solving for MM (molar mass):

MM = grams*R*T/(*L)

MM = (1.41g*62,3636torrL/molK*298K)/(1.86torr*0.1L)

MM = 1.41 x 105 g/mol

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