## anonymous one year ago Help with combustion?

1. anonymous

Has anyone done the combustion assignment for chemistry on flvs?

2. anonymous

For example I have to find out the reaction type of Fe2O3 + CuSO4, and I said combustion/synthesis.

3. Astrophysics

A combustion is as follow $C_xH_y + O_2 -> CO_2+H_2O$

4. Astrophysics

Your reaction type would be a double replacement

5. Astrophysics

Here I'll make you a simple summary of the reactions

6. anonymous

CO2 + H2O is only if it's a hydrocarbon combusting, no?

7. Astrophysics

$AB -> A+B ~~~(decomposition)$ $A+B -> AB ~~~~(composition/ synthesis)$ $AB+C -> AC+B ~~~ \text{(singe replacement, depends upon metal and nonmetal)}$ $AB+CD -> AD+CB ~~~~(double~replacement)$ and you have the combustion reaction above

8. anonymous

Oh alright. So I'd be right in saying that Pb(NO3)2+ KI is combustion/single replacement?

9. Astrophysics

Note, for double replacement, A and C are metals B and D are non metals

10. Astrophysics

Those are not combustions

11. Astrophysics

A single replacement sounds good though

12. anonymous

How do I tell if it's a combustion or not if oxygen is present?

13. Astrophysics

Well I haven't taken too much chemistry but a combustion is in the form of $C_xH_y + O_2 -> CO_2+H_2O$

14. anonymous

That's only hydrocarbon combustions. inorganic molecules combust as well.

15. Astrophysics

This is the general form of a combustion reaction, what you're thinking of is, that in general anything with oxygen can be considered combustion.

16. Astrophysics

That's why there is a general form of the equation to avoid confusion

17. anonymous

So the general form of combustion only includes carbon+hydrogen and oxygen?

18. Astrophysics

Yes, generally we say combustion is the reaction of oxygen with an compound of carbon and hydrogen

19. anonymous

20. Astrophysics

Well let me tag someone else who's better at chemistry that may be able to explain this @empty

21. anonymous

Alright. Thank you for your help! I appreciate it.

22. Astrophysics

23. anonymous

What do you think nincompoop?

24. nincompoop

Fe2O3 + CuSO4 do you want to figure what kind of reaction will take place?

25. anonymous

Yes. Also, what determines if it will be a combustion if not just having oxygen present?

26. anonymous

So the undermentioned reaction is combustion?

27. anonymous

Is there a rule of exception?

28. anonymous

*aforementioned

29. nincompoop

correct

30. anonymous

As well as double replacement?

31. Astrophysics

Definitely a double replacement

32. nincompoop

Fe2O3 + CuSO4 ye double replacement

33. anonymous

Ok, one more for practice.

34. nincompoop
35. anonymous

Mg+Hcl would be single replacement, but not combustion because there's no oxygen?

36. nincompoop

correct

37. anonymous

HCl*

38. nincompoop

but you have to take note that Oxygen is abundant in the atmosphere and it is difficult to do these experiments in an environment where there is no oxygen the rule of thumb is that whenever there is an addition of oxygen, that is a combustion reaction

39. nincompoop

but in the cases of your problem, it is more important to know single replacement, double replacement, redox reaction (a type of combustion and can have no oxygen in the equation), decomposition and synthesis. later on in your chemistry experiences, these names do not matter much because you will be focusing on movement of electrons for the most case.

40. nincompoop

use the formula that astro provided you and usually you can pretty much tell or make a good guess with the number of substances present in the reaction

41. Astrophysics

$Fe_2O_3+3CuSO_4 ->Fe_2(SO_2)_3+3CuO$

42. nincompoop

there is nothing more to it, and you will be focusing more on balancing equations and calculating enthalpy, spontaneity, gibbs free and other exciting things about chemistry

43. Astrophysics

Mhm

44. Astrophysics

Is that still considered a combustion

45. nincompoop

the SO will be treated as on compound $$\sf (SO_4)$$

46. Astrophysics

oh oops that should be SO_4 but yeah

47. anonymous

Noted 'poop. Does SO_4 being treated that way change whether it's a combustion or not?

48. nincompoop

which should have been covered in other lessons like lewis structures, ground charge and formal charges.

49. nincompoop

nah it is minute and shouldn't be the focus of concern

50. nincompoop

oxygen makes everything combustible and very reactive, let us just put it that way

51. anonymous

OK. I think I got it. You've all been tremendous help. I really appreciate it. Just curious though, what do you guys do for a job (school maybe)?

52. anonymous

Professional amphibian lawyer/politician.

53. anonymous

Well see you later 'gater.

54. nincompoop

woodward gives a good way to capture these concepts do not shy away from asking him LAUGHING OUT LOUD

55. anonymous

OK. Is there anything that you think I don't understand or that wasn't covered thoroughly enough you feel, woodward?

56. anonymous

Actually this is unbalanced: $C_xH_y + O_2 -> CO_2+H_2O$ Nope, nothing really to add really, only because chemistry has too much to say about everything lol

57. nincompoop

:) I was hoping someone will see that

58. nincompoop

hahaha

59. Astrophysics

It's just a template/equation reason why it's CxHy

60. anonymous

medal + fan if you can balance it before me. :)

61. anonymous

Oh, beat me to it! How do I reward everyone for the help?

62. nincompoop

do it

63. anonymous

The balance? Well, assuming C_1H_1, then...

64. Astrophysics

You click "best response" which gives the user a medal, unfortunately you can only pick 1.

65. Astrophysics

Try CH4 methane

66. anonymous

Alright

67. anonymous

I think this is it: $4C_xH_y + O_2 \rightarrow 4x CO_2+2yH_2O$

68. anonymous

CxHy+O2−>CO2+H2O CH4+4O2 -> CO2 +2H2O I guess

69. anonymous

Wait

70. anonymous

2O2*

71. Astrophysics

When you're balancing a combustion like that, do it in this order, CHO

72. anonymous

Yeah my answer is clearly wrong, there's no coefficient on $$O_2$$!

73. anonymous

Well thanks guys! I've chosen Astro as best response because of consistent attendance and great help.

74. Astrophysics

Let me correct your eqatuon Professor

75. Astrophysics

For CH4 and we can conclude then :-)

76. Astrophysics

$CH_4 + 2O_2 -> CO_2+2H_2O$

77. anonymous

I corrected it to that I think :)

78. Astrophysics

Ok great!

79. Astrophysics

Sorry I didn't see that post haha, well done!

80. anonymous

Alright I'll be off then! Thanks guys!

81. Astrophysics

Np, take care!