Question

Dear Scientist, Congratulations! You and your group have been selected for the contract job of designing my company’s latest product. We are working to a tight schedule so your product must be finished A.S.A.P. The product is a drinks can that, when desired, can be activated to cool the drink it contains wherever the user may be at the time. In the first instance we are looking for a product that can cool 100 cm3 of drinkable water by 5 q C in no more than 5 minutes. Try not to exceed this temperature change as we do not want our customers’ teeth to freeze! You and your team will need to use your knowledge of chemistry to come up with a product design which includes full details of the cooling process with exact quantities of any chemicals used and time periods required to give us our desired –5 q C temperature change. We would like you to provide us with both theoretical and experimental quantities for any chemicals used in order for us to evaluate the effectiveness of your design. In order to pass the strict requirements of the Food Standards Agency it is also imperative that the cooling process is safe. We at the department have done a little research ourselves and have found two chemicals that we think would be useful; ammonium chloride (NH4Cl); solubility 37.2 g / 100 g water, £2.55 per 500 g ammonium nitrate (NH4NO3); solubility 192 g / 100 g water, £10.95 per 500 g Please include with your final product design an explanation of which chemical you decided most suitable and why, including careful consideration of the Health and Safety implications of your chosen design. Finally we need to know that you have successfully tested your design. Please provide data to indicate this. Thank you for accepting this contract and we look forward to seeing your results.

Your write-up should include:

- The chemical reaction (formula) that will result from the chemical(s) you are suggesting Bettie's Beverage Company use

- The change in temperature that will result from the chemical reaction.

- What quantities of chemical(s) and water to use for your cooling reaction, how much it would cost, and why you chose the chemical(s) you are suggesting for Bettie's Beverage Company.

- Your justification for choosing a particular chemical (or chemicals) should be based on:

(1) How much chemical would need to be used (remember - chemicals cost money to buy!)

(2) The amount of cooling produced (remember - too much cooling causes a health hazard to the consumer!)

HINT:

q = m x C x (delta T), where q = energy (J), m = mass (g); C = the heat capacity of water = 4.18 J / (degrees C * g); and delta T = the change in temperature (degrees C)

Hsolv = the molar energy of solution = the net energy generated by dissolving a salt powder into water = kJ/mol

Answer 1