Question

1. Reaction rates are greatly affected by temperature. As a rule of thumb, the rate doubles for every 10°C increase in temperature.

Following this rule, what would the rate be at 55 °C if the rate was 3.1 x 10-3 M sec -1 at 25 °C ?

Hints:

• What is the temperature difference between 25 °C and 55 °C?

• If the temperature doubles each time the temperature rises 10 °C, how many times will the rate double?

2. If it took 4.5 hours to travel 385 km, what would have been the average rate of travel in meters per second?

3. From stock solutions, the following amounts of reagents were measured and then mixed: 10.0 mL of 4.08M CH3COCH3 , 10.0 mL of 0.0022M I2 , 10.0 mL of 1.1M HCl and 10.0 mL of H2O.

What would be the initial concentration (mol/L) of hydrogen ions?

Hints:

What is the total final volume? To find it, you need to add together the volumes of all solutions and additional water added.

The initial concentration is the amount of the solute present at the time of mixing assuming there is an instant just before the reaction starts.

Find the moles of hydrogen ions in 10.0 mL of 1.1M HCl, then divide it by the final volume.

Answer 1

Change in temperature = (55 - 25) = 30⁰ c.

Rate double by 10⁰c rise .

Hence , in 30⁰c , the rate is doubled by 3 times.

Hence, final rate when temperature in increase by 30⁰c will be

= Initial rate × 2³

= 3.1×10^-3 × 2³

= 2.48×10^-2 M sec^-1 .

2.

Average rate

=   × × ×

= 23.76 m/s.

Hence, aversge rate us 23.76 meters/sec.

3.

mmoles of HCl = molarity of HCl × volume of HCl

= 10× 1.1 = 11 .

Total volume of solution

= 10.0+ +10.0 + 10.0 + 10.0 = 40.0 mL.

[ HCl ] = [H⁺] = ( mmoles of HCl/total volume)

= ( 11/40)

= 0.275 (mol/L).