calcium with water and ammonium chloride with water?

Question

XD
i have quite a few questions i want to ask and check over with like little things like states and stuff xd if anyones not that busy have a look!

1)Ca(s)+ 2H2O(L)>Ca(OH)2 (aq)+H2(g)
Nh4cl (s)+ h2o> NH4cl(aq)? have no idea on that

2)to find molar ethaply for calcium of water
i do n= mass/molar mass to get moles for ca
do q=mc T to get heat for water
then molar ethaply is q/ moles of ca
i have all the values but those are the right steps?

it will be same for NH4CL(ammonium chloride)

3) and dissoultion of ammonium chloride with water is endothermic becasue heat was absorbed since the final temperature went down

4)if more calcium was added to the calcium with water reaction.. what will happen to molar entaply? it will go down since the entaply is going to be divided by a higher number right

5) this question was asking for heat or enthaply change of both equations.. i think (heat and enthaply change is the same thing right)

to get q its just mc delta T right

6) i have no idea how to write thermal equations for both of em so help here will be nice xd

7)calcium with water is exothermic becasue heat was produced on the products side(temperature increased) ammonium chloride with water is endo cuz heat was absorted final temperature lowered
but i think this question was worth 6 marks.. i dont know how i can do a 6 mark answer

Answer 1

Since you have not present the problem itself, so I can not make any judgment wether you have answered the question correctly or not. I can only check to see if your logic and reasoning is alright or not.
(1) Right.
(2) You mean enthalpy, right?
I think you missed the work done by the "system". Remember, H(S,p) = U + pV. You have rightly considered the U part. But H2 is released and it did work by pushing away the air of its volume. Assume the surrounding is at constant pressure, the work done is:
p(Vf - Vi) = (delta)nRT, where n is the moles of released H2, and is the same as the moles of Ca reacted.
(3) Right.
(4) Molar enthalpy does not change, unless the reaction is incomplete. In the second case it would be dissolution.
(5) I am not so sure about "heat". Are you talking about "U"? See my point in (2).
(6) normally is to write out the "reaction" and (delta)H for one mole.
(7) Right.

Answer 2

some blatent wrong answers there, 25% chance of guessing the right answer but you actually chose the most soluable, that is potassium nitrate. The above person is totally right^^ with calcium carbonate.