If you dissolve 10.0 g of compound X in 100 0 mL of distilled water, the liquid

Question

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 24degree C for 10 minutes. Why would you not want to sell a cold pack made with compound X? Consider a beaker of water that has an initial temperature of 25 degree C When an ionic salt is dissolved in the water, the temperature changes to 5 degree C. If you were to touch the beaker, what would you feel? Is this reaction endothermic or exothermic? Is the energy of the products higher or lower than the energy of the reactants? Two competing corporations are submitting data to the US Military to create chemical hot packs. The Military has stipulated that the each hot pack may cost no more than 85 cents and must result in at least a 20 degree C rise in temperature when activated. Which of the following companies is the Military going to hire?

Explanation / Answer

3)

1. Technically it depends upon the temperature of your hand: if we assume the body temperature is 37 C then your hand is warmer than the beaker and the beaker will feel cold.

2. This is an endothermic reaction.

3. If the beaker changes from 25 C to 5 C the energy is lower.

4) answer : company B

Compound A.

How much is needed? That's

1.5g x (20/5) = 6.0 grams.

Cost of 6.0 g is

$184.04 x (6.0/1000) = about $1.10 each.

its cost = 110 cents

Compound B the same way.

1.0g x (20/2.5) = 8.0 grams.

Cost of 8.0 g is

$97.13 x (8.0/1000) = about $0.777 each.

its cost 77.7 cents.

so the company hire company B. because it pays no more than 85 cents.

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