Question

When an AgNO3 solution is treated with 50.0 mL of HI gas to give 0.235 g of AgI, what is the temperature of the HI gas?

Answer 1

If the pressure of the gas is 1.00 atm, its temperature is 335 °C.

The steps to follow are:

1. Write the balanced chemical equation.
2. Convert grams of AgI → moles of AgI → moles if HI.
3. Use the Ideal Gas Law to calculate the temperature of the gas.

Step 1

AgNO₃ + HI → AgI + HNO₃

Step 2

0.235 g AgI × `(1"mol AgI")/(234.8"g AgI") ×(1"mol HI")/(1"mol AgI")` = 0.001 001 mol HI (3 significant figures + 1 guard digit)

Step 3

`PV = nRT`

You haven't given the pressure of the HI. I assume that it is 1 atm.

`T = (PV)/(nR) = (1.00"atm" × 0.0500"L")/(0.001001"mol" × 0.08206"L·atm·K⁻¹mol⁻¹")` = 608.8 K

= (608.8 – 273.15) °C = 336 °C (3 significant figures)

This seems like a high temperature for the gas. If it had a different pressure, you will have to recalculate.

Here's a flow chart giving the general strategy for stoichiometry problems.