Chemistry 2720 Fall 2000 Assignment 2

Due: Tuesday, Sept. 26, 9:25a.m.

1.

Calculate the total enthalpy change for the stoichiometric conversion of 20g of gaseous carbon dioxide to carbonic acid ( H₂CO_3(aq)) by reaction with liquid water. [5 marks]

2.

The ideal gas law is only approximately correct. One alternative commonly used to describe real gases is the virial equation:

$$P\bar{V} = RT\left(1 + \frac{B_1}{\bar{V}} + \frac{B_2}{\bar{V}^2} +\ldots\right)$$

If we take $B_1=B_2=\ldots=0$, we recover the ideal gas equation. By taking more and more correction terms, we obtain increasingly accurate representations of the behavior of a real gas.

(a)

Calculate the work done per mole when an ideal gas expands isothermally and reversibly at 273K by a factor of 20. [3 marks]

(b)

For carbon dioxide, $B_1 = -1.497\times 10^{-4}\,\mathrm{m^3/mol}$ at 273K. Assuming that the higher-order virial coefficients (B₂, B₃, etc.) are all negligibly small, calculate the work done per mole when carbon dioxide expands isothermally and reversibly at 273K from 22 to 440L/mol (a twenty-fold volume increase). Would it be appropriate to treat carbon dioxide as an ideal gas in this situation? [10 marks]

3.

A 300g iron block is heated to $150^\circ\mathrm{C}$ and then placed in a sealed adiabatic container with 800g of water initially at $20^\circ\mathrm{C}$. What is the final state of the system? Assume that the pressure is roughly constant at 1atm so that water boils at its normal boiling point. [10 marks]

4.

Suppose that 25g of sodium hydroxide is dissolved in 200mL of water at $25^\circ\mathrm{C}$. What is the temperature change? According to your calculation, would any special precautions be necessary in preparing this solution? [10 marks]