Achieve Q8

[Jessy Ji 2J]

Hi, I have trouble figuring out this problem. Can somebody help me please. Do I need to find the molar heat capacity from a table or something?

Carbon disulfide can be prepared from coke (an impure form of carbon) and elemental sulfur.

4C(s)+S8(s)⟶4CS2(l) deltaH=+358.8 kJ

Calculate the amount of heat absorbed when 1.66 mol S8 is reacted at constant pressure.
Calculate the amount of heat absorbed in the reaction of 151 g of carbon with excess sulfur.
Calculate the amount of CS2 produced when 375 kJ of heat is absorbed.

[Ethan Mai 1D]

You can solve this problem using stoichiometric techniques!

For the first question, we can derive from the chemical equation that there are 358.8 kJ absorbed per 1 mol of S8 used up. Therefore, convert the moles of S8 to the amount of kJ.

For the second question, we can also see that there is are 358.8 kJ absorbed per 4 moles of C used up. Therefore, convert the grams of C to moles of C, and convert the moles of C to the amount of kJ absorbed.

For the third question, we note that there are 358.8 kJ of energy absorbed for every 4 moles of CS2 produced. Therefore, we convert 375 kJ to moles of CS2, and convert that figure into grams if needed.

I hope this helps!

[Kiku Shirakata 2A]

Hello,

You can use stoichiometry to determine each answer. For part a, you can multiply the delta H by 1.66 moles to figure out the heat absorbed for 1.66 moles of S8 instead of 1 mole as given. Part b is the same process but you have to complete an extra step to convert grams of carbon to moles of carbon. Also, it is important to notice that the delta H is given for 4 moles of carbon, so you need to take that into consideration. Lastly, for part c, you need to divide the given delta H by 375 kJ and multiply by 4 moles to determine how many moles of CS2 can be produced when 375 kJ of heat is absorbed. Then, convert moles to grams.

Hope this helps!