Wk 3&4 Achieve Q5

[Jessy Ji 2J]

Hi, for the thermochemistry achieve problem 5, I multiply the third equation by three and added to the first equation. I keep getting 6397 for my answer. But it is not correct. Can someone help me out please. Thank you.

[Riya Sawhney 1C]

Hi, to get the correct answer you will need to use all of the chemical equations given, but will not necessarily have to manipulate all of them. Remember to pay attention to phases!

[Rachel Fox - 3F]

For this problem, you are going to want to manipulate each equation in order to get everything on the right side and with the right stoichiometric coefficient. When you multiply the reaction by a certain coefficient, you do the exact same thing to the enthalpy. The total enthalpy is the sum of the individual enthalpies of the reactions since enthalpy is a state function. So, you will use the enthalpy of the first reaction, multiply the enthalpy of the second reaction by 6, multiply the enthalpy of the third reaction by 3, and multiply the enthalpy of the fourth reaction by -2 to get your answer.

[Kiku Shirakata 2A]

Hello,

For this problem, we will use Hess's Law. We need to figure out how to manipulate the given reactions so that they cancel out and add to the final reaction that we want. First, set up the combination of reactions that give you the final reaction. If we multiply the given reaction to get certain coefficients, we also have to multiply the delta H value, and if we reverse the reaction, then delta H changes signs. Finally, add all the delta Hs together to determine the final delta H for the resulting reaction.

Hope this helps!

[Crystal Ma 2J]

Hi, you have to use all the equations given! What i did was use the 1st equation (-600 kJ) and manipulate the second (-74.8 kJ*6) to replace HCl(aq) with HCl(g). Then, I manipulate the third equation (-1845*3) to get 2M(s)+3Cl(g)--> 2Cl3(aq); finally, i manipulate the last equation (480 kJ*2) by reversing it and add that to the result i previous got. By adding -600+(-74.8*6)+(-1845*3)+(480*2), you get -5623.8 kJ