Question

9.) As mentioned below, you are required to design your own procedure for determining the heat of dissolution of your chosen salt with a coffee cup calorimeter. Answer the following questions and consider them in designing this procedure:

a.) When you find your initial temperature Ti, should you take one measurement from the thermometer as soon as you place it in the water in the calorimeter? Why or why not? If not, what should you do instead?

b.) Do you expect the temperature of the water in the calorimeter to rise, fall, or stay the same after you add your salt? If the temperature will change, will it continue to change indefinitely or not?

c.) How will you know your dissolved salt solution has reached it's maximum or minimum temperature, i.e. what will you observe in your data to indicate this has happened?

d.) Should you repeat your experiment? Why or why not? If so, what could you change from trial to trial? (Think about what parameters you have control over and remember that you're trying to optimize your system!). Give two possible suggestions. Should you change both or just one? Which one would be easier to change from trial to trial?

Answer 1

Q (a) to note the initial temperature T1 of water in the calorimeter , put the thermometer in it and wait for some time to get constant temperature. we should not note the temperature as soon as u place it in calorimeter.

(b) after we add a salt the temperature may rise or fall depnds on the type of the salt.for example the temperature will rise with NaOH but decreases with the KCl.. the temperature will not change indefinitely rather changes upto a certen temperature , which actually depends on how much energy is released or abserbed by the salt.

(c) we have to wait for some time after adding the salt till we get an equilibrium temperature. which indicates the final temperature.

(d) yes we have to repeat the experiment to get the water equivalent of the calorimeter . we can do that with hot water (T₂)and the cold water (T₁). find the final temperature (T₃) after mixing the two .

Heat lost by the HOT water = Heat gained by the cold water + heat gained by the calorimeter