4D1

Moderators: Chem_Mod, Chem_Admin

JChen_2I
Posts: 107
Joined: Fri Aug 09, 2019 12:17 am

4D1

Postby JChen_2I » Mon Jan 27, 2020 11:48 pm

Carbon disulfide can be prepared from coke and elemental sulfur:
4C(s)+S8(s) --> 4CS2(l) deltaH=+358.8kJ
(b) Calculate the heat absorbed in the reaction of 197g of carbon with an excess of sulfur.

Can someone explain why we have to divide by 4 moles of carbon to get the answer? And should we normally assume deltaH is giving in kJ/mol?

Benjamin Feng 1B
Posts: 102
Joined: Sat Sep 07, 2019 12:19 am

Re: 4D1

Postby Benjamin Feng 1B » Tue Jan 28, 2020 12:04 am

You need to divide by 4 since there are 4 moles in the product side, which means that when you form 4 moles of the product, 358.8 kJ is released. That means when 1 mole is formed, only 358.8/4 kJ of energy is released. You want the coefficient of the product you are interested in to be 1. Delta H is given in joules, assuming that the reaction occurs in units of moles.

Amy Xiao 1I
Posts: 101
Joined: Sat Jul 20, 2019 12:15 am

Re: 4D1

Postby Amy Xiao 1I » Wed Jan 29, 2020 9:18 pm

The way the solutions manual solves it is that it first converts the 197 g of Carbon to mols -> 16.40 mol C. It also divides the energy absorbed by 4 moles of Carbon by 4 so that you will know how much 1 mol Carbon absorbs. After that, you can just multiply that energy by however many moles of carbon you need to use.


Return to “Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)”

Who is online

Users browsing this forum: No registered users and 2 guests