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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: Craig65 on March 17, 2019, 12:03:10 PM

Title: old fart trying to understand chemistry :-)
Post by: Craig65 on March 17, 2019, 12:03:10 PM

How would I work this out? I want to know how to do the calc not just get an answer.. with thanks Craig

If the Heat of Combustion of Benzene (C6H6) is 4.25MJ per mole; How  much heat can I expect to be released if I burn 100g of Benzene knowing that the Combustion Efficiency is only 80%.

Title: Re: old fart trying to understand chemistry :-)
Post by: Mitch on March 17, 2019, 12:22:29 PM

The first step will be converting grams of benzene to the units of moles of benzene. Can you do that? Hint, you'll need to know benzene's molar mass to figure it out.

Title: Re: old fart trying to understand chemistry :-)
Post by: Craig65 on March 18, 2019, 05:51:19 AM

1 mole of Benzene = 0.012802156497658 *100g = 1.2802156497658 mol

Title: Re: old fart trying to understand chemistry :-)
Post by: Craig65 on March 18, 2019, 05:55:47 AM

therefore 100grams of Benzene = 1.2802156497658 * 4.25mj * .8 = 4.35273320920372 mj ?
Thanks

Title: Re: old fart trying to understand chemistry :-)
Post by: AWK on March 18, 2019, 06:56:46 AM

4.25, 100, 80
4.35273320920372
How many significant digits you should use in the final result (remember about rounding rules)?