Release of Heat in kJ - Immediate Help Needed

[PeanutBrittle]

I am struggling with a recent chemistry lesson. Immediate help is needed and would be greatly appreciated. I know that we have to first find the limiting reagent, and then go on to determine the heat released in kiloJoules.

Homework Statement

How much heat will be released when 4.72 g of carbon reacts with excess O2 according to the following equation?

Homework Equations

C + O2 --> CO2 (Delta) H = -393.5 kJ

The Attempt at a Solution

 

[mgb_phys]

How many moles of C are there in 4.72g?
The equation says you get 393.5kJ for each mole.

 

[Blueshift5]

Hi there,

I understand that you are struggling with a recent chemistry lesson and need immediate help. Let me try to guide you through the problem and hopefully it will help you understand the concept better.

First, we need to find the limiting reagent in the reaction. This is the reactant that will be completely used up and therefore determines the amount of product that can be formed. In this case, we have 4.72 g of carbon and excess oxygen. To find the limiting reagent, we need to convert the mass of carbon into moles. This can be done by dividing the mass by the molar mass of carbon, which is 12.01 g/mol. This will give us 0.393 mol of carbon.

Next, we need to convert the amount of carbon into the amount of oxygen needed for the reaction. From the balanced equation, we can see that for every 1 mole of carbon, 1 mole of oxygen is needed. Therefore, we need 0.393 mol of oxygen.

Now, we compare this amount to the amount of oxygen we have, which is excess. If the amount of oxygen we have is greater than 0.393 mol, then it is not the limiting reagent. However, if it is less than 0.393 mol, then it is the limiting reagent. In this case, we have excess oxygen, so we can move on to determining the heat released.

To find the heat released, we use the formula Q = n * Delta H, where Q is the heat released, n is the amount of limiting reagent in moles, and Delta H is the heat of reaction, which is given to us as -393.5 kJ. Plugging in the values, we get:

Q = 0.393 mol * -393.5 kJ/mol = -154.6 kJ

Therefore, the heat released in this reaction is -154.6 kJ. I hope this helps you understand the concept better. If you have any further questions, please feel free to ask. Good luck with your studies!