Question

Для тетрахлорметана Δ H° = 30,0 кДж/моль. Рассчитайте q, w, Δ H и Δ U, когда 0,75 моль CCI4 испаряется при 250 К и 1 бар. Я все рассчиталa, но не знаю, как рассчитать работу w. Пожалуйста помоги!

Answer 1

Ответ:
Δ H = q + w = qp - wv
ΔH = ΔH° + ΔngRT
Δng = 1 - 0 = 1

ΔH° = 30,0 кДж/моль

R = 8,314 Дж/моль К

T = 250 К
ΔH = (1 моль) (8,314 Дж/моль К) (250 К) + (30,0 кДж/моль) = 32,87 кДж.
w = -PΔV
PV = nRT
V = nRT / P = (0,75 моль) (8,314 Дж/моль К) (250 К) / (1 бар) = 1541,49 мл.
w = - PΔV = -(1 бар) (1541,49 мл - 0) = -1541,49 Дж.
q = ΔH - w = 32,87 кДж - (-1541,49 Дж) = 34,4 кДж.
ΔU = q - PΔV
ΔU = (1 моль) (8,314 Дж/моль К) (250 К) + (30,0 кДж/моль) - (1 бар) (1541,49 мл) = 19,09 кДж.
Таким образом, q = 34,4 кДж, w = -1541,49 Дж, ΔH = 32,87 кДж и ΔU = 19,09 кДж при испарении 0,75 моль тетрахлорметана при 250 К и 1 бар.

Answer 2

Calculation of q, w, ΔH, and ΔU for the vaporization of CCl4

To calculate the values of q, w, ΔH, and ΔU for the vaporization of CCl4, we can use the following equations:

1. q = ΔH + PΔV 2. w = -PΔV 3. ΔU = q + w

Given data: - ΔH° = 30.0 kJ/mol - n = 0.75 mol - T = 250 K - P = 1 bar

To calculate q, we need to determine ΔV, the change in volume during vaporization. Since CCl4 is a liquid, we can assume its molar volume is constant during vaporization. Therefore, ΔV can be approximated as the molar volume of CCl4 in the liquid state.

To calculate ΔV, we can use the ideal gas law:

PV = nRT

Rearranging the equation, we get:

V = (nRT) / P

Substituting the given values, we can calculate V:

V = (0.75 mol * 0.0831 L·bar/(mol·K) * 250 K) / 1 bar

Now that we have V, we can calculate q using the equation:

q = ΔH + PΔV

Substituting the given values, we get:

q = 30.0 kJ/mol + (1 bar * V)

To calculate w, we can use the equation:

w = -PΔV

Substituting the given values, we get:

w = -(1 bar * V)

Finally, we can calculate ΔU using the equation:

ΔU = q + w

Substituting the calculated values, we get:

ΔU = q + w

Now let's calculate the values:

1. Calculate V: V = (0.75 mol * 0.0831 L·bar/(mol·K) * 250 K) / 1 bar

2. Calculate q: q = 30.0 kJ/mol + (1 bar * V)

3. Calculate w: w = -(1 bar * V)

4. Calculate ΔU: ΔU = q + w

Please note that the calculations provided above are based on the given data and assumptions.