Question

2) (2 pts) If you dissolve 10.0 g of compound X in 100.0 mL of distilled water, the liquid turns red. The temperature of the liquid stays at 24 °C for 10 minutes. why would you not want to sell a cold pack made with compound X? 3) Consider a beaker of water that has an initial temperature of 25 °C. When an ionic salt is dissolved in the water, the temperature changes to 5 °C. a. (1 pt) If you were to touch the beaker, what would you feel? b. (1 pt) Is this reaction endothermic or exothermic? C. (2 pt) Is the energy of the products higher or lower than the energy of the reactants? 4) (10 pts) Two competing corporations are submitting data to the US Military to create chemical hot packs. The Military has stipulated that the each hotpack may cost no more than 85 cents and must result in at least a 20 °C rise in temperature when activated. Which of the following companies is the Military going to hire? Corporation Chemical Data Submitted to Military Cost of Chemical Company A 1.5 g of Y results in a 5°C rise in temperature $184.04/ kg Company B 1.0 g of Z results in a 2.5°C rise in temperature $97.13/kg

Answer 1

2.Since the temperature of the solution remains constant for a long period of time and does not decrease upon adding compound X, we cannot make a cold pack out of compound X.

3. (a) Since the temperature of the beaker decreases upon adding the salt, the beaker would feel cold to the touch.

(b)Since, the temperature decreases, it implies that the solution absorbs heat. Hence,this is an endothermic reaction.

(c) Since the products are formed after absorbing heat, the energy of the products are higher than the energy of the reactants.

4.The military is going to hire Company B because Company B provides a hot pack which costs less than 85 cents when calculated as below.

Costwise,it can be compared as follows

Company A: 1.5g of Y results in 5 degree celcius rise in temperature. Thus, for 20 degree rise in temperature,[(1.5/5)*20] = 6g of Y is required. 6g of Y costs [(184.04/1000) *6] = 1.10 dollars

Company B : 1g of Z results in 5 degree celcius rise in temperature. Thus, for 20 degree rise in temperature,[(1/2.5)*20] = 8g of Z is required. 8g of Z costs [(97.13/1000) *8] = 0.77 dollars = 77 cents , which is less than 85 cents.

Hence, company B is hired by the military.