Achieve 7 (Week 5)

[asheagg3I]

Hi,

Can someone explain how to calculate Hrxn? Is there an equation that we should be using?

[Vicky Tong 3E]

Hi! For this question, you're going to need to look at the Hf values for each molecule (the first column). For instance, CO2(g) is –393.5 kJ/mol. Continue finding the rest of the enthalpy values, and then multiply each enthalpy by the coefficients present in the reaction. For example, if CO2 has 3 mols, you would multiply –393.5 x 3. Afterward, you will subtract products - reactants to reach the final enthalpy change.

[Meghan Spoeri 2D]

The equation you use is Delta H = sum of Delta H formation (products) - (sum of Delta H formation(reactants)). you can find the delta H of formation for each individual product and reactant on the table under Delta Hf.

[Kathleen Wijaya 3L]

You should use the equation ∆Hrxn=∆Hf(products)-∆H(reactants)

[Kathleen Wijaya 3L]

You should use the equation ∆Hrxn=∆Hf(products)-∆H(reactants)

[Diana Avalos]

The equation you should use here is ΔH_RXN=ΔH_f(products)- ΔH_f(reactants)

[005502505]

∆Hrxn=∆Hf(products)-∆H(reactants) is the equation you'd use, in this instance. Hope this helps!!

[Shannon Lau 14B - 1H]

Because you are trying to find the enthalpy change = delta H of reaction = Delta H of product - Delta H of reaction. To find Delta H of the product you multiply the standard enthalpy values for each chemical (found on the list that is given in the problem - just click on the link) by the amount of it (as seen in the stoichiometry - # of moles each has). It is the same thing for Delta H of reaction but obviously just looking at the reaction side. You subtract the two to find the amount of enthalpy change.

Keep in mind to label everything/use units so that you can cross it out along the way so you can make it clear to yourself why the final units should be kJ.

[Heba Bounar 3K]

Hi! For this problem, you should use enthalpy of formation values to find deltaHrxn. Use the formula Delta H = sum of Delta H formation (products) - sum of Delta H formation(reactants) using the standard enthalpy of formation values for reach reactant and product. Hope that helps!