Question

hello guys, is 2Ca(s) +O2(g) -> 2CaO(s) and exothermic or endothermic reaction? & what is this chemical reaction called (eg. neutralisation, decomposition)? or it does not have one.
Thanks in advance

Answer 1

combination rxn. A + B --> AB, You need bonds broken - bonds formed to determine exothermic of endothermic

Answer 2

or*

Answer 3

endo? cause bond forming (:

Answer 4

not necessarily

Answer 5

mhmm, but its a mcq question.
Which one of the following reactions would you expect to be endothermic?
A 2CO)g) + O2 (g) -> 2CO(g)
B KOH(aq) + HCL(aq) ->KCl(aq) + H2O(l)
C 2Ca(s) +O2(g) -> 2CaO(s)
D Cl2(g) -> 2Cl^- (g)

Answer 6

dont mind tell me whats the reaction is called for option D? thanks.

Answer 7

redox rxn.

Answer 8

oh thank you. so whats the answer for the qn? since i know A & B is out. and option C could be both endo and exo. so is the ans D? O_O

Answer 9

why are a and b out? D is definitely not exothermic. Cl2 is chlorine's elemental state and it would take a lot of energy the separate Cl2 into Cl-

Answer 10

mhmm aint neutralistion and combustion exothermic??

Answer 11

not necessarily but if you are asked to assume so then chose the answer that goes with those assumptions but know that is not always the case in reality

Answer 12

(that neutralization and combustion rxns are exo)

Answer 13

so which one is endo T.T

Answer 14

or you're not sure as well? o_o >_>

Answer 15

There is no way to tell with the information you are given unless you proceed under some assumptions

Answer 16

so the question was not set properly? :o

Answer 17

there are probably some assumptions your teacher mentioned you are forgetting

Answer 18

nooo its a mcq question from a book.

Answer 19

is there an appendix for you to look up the bond enthalpies

Answer 20

shoot. that page fall off and its missing. ahh, clumsy me.
Thanks anyway (:

Answer 21

A 2CO)g) + O2 (g) -> 2CO2******(g)
B KOH(aq) + HCL(aq) ->KCl(aq) + H2O(l)
C 2Ca(s) +O2(g) -> 2CaO(s)
D Cl2(g) -> 2Cl^- (g)