# Write a balanced equation? C3H8 + O2 --> CO2 + H2O [These numbers are subscripts.]?

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very easy.

2C3H8+7O2 --> 3CO2+8H2O

C 3/6 C2/6

H 8/16 H2/16

O 2/14 O3/14

I find it works if you add up how many of each lelment you have on the bottom, and as you add numbers and the multiply against the subscripts, to keep a running tally. I hope this helps you out. This kind of thing is hard to show work on. :)

Source(s): I have taken Quantitative Physical Sci.
• 5 years agoReport

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• C3H8+ 5O2 -> 3CO2 + 4H2O

As you can see is a more math problem than a chemistry

problem.

The key is the C3H8 because there we have 3 C and 8 H = 4H2 which must be found at the right side of the equation.

That's why we put 3 before CO2 and 4 before H2O.

If you add all the O at the right side you will find 10 O =5O2

and thats why we put 5 at the left side before O2.

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• Anonymous

There is a nice trick to write the oxidation of hydrocarbons.

lets c...

C3H8 has 3 carbon atoms. thus it will give 3CO2 on burning.

C3H8 has 8 H atoms. thus it will give 4(half of 8) H2O atoms.

Now balance the oxygen by seeing.

thus the balanced Rxn is ::

C3H8 + 5O2 ------------->> 3CO2 + 4H2O

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• For the best answers, search on this site https://shorturl.im/axB9d

Now can someone balance this please? MgCl2 + NaCO3 --> MgCO3 + NaCl Yes, I can, but you need to get the correct formulas written first. That may be part of the reason you can't balance it. Sodium carbonate is Na2CO3, not NaCO3. Here is the correct equation: MgCl2 + Na2CO3 --> MgCO3 + 2NaCl If you were in my class, I would also make you include the state symbols. Impress your teacher and do that. MgCl2(aq) + Na2CO3(aq) --> MgCO3(s) + 2NaCl(aq) Now you can see what is actually driving this double replacement reaction. It is the formation of an insoluble product. In this case magnesium carbonate.

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• OK that person (2nd answerer) that said very easy is wrong, just so you know. Combustion equation(not like that's relevant at all)!

Start: C3H8+O2 --> CO2 + H2O

> 3C1

> 8H2

> 2O3

C3H8+O2 --> 3CO2 + H2O

> 3C3

> 8H2

> 2O7

C3H8+O2 --> 3CO2 + 4H2O

> 3C3

> 8H8

> 2O10

Final: C3H8+5O2 --> 3CO2 + 4H2O

> 3C3

> 8H8

> 10O10

Get it?

Hope this helps!

Source(s): My Chem Class
• Mike6 years agoReport

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