ETHANOL QUESTION (1 Viewer)

hscwav2012

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This is from Independent 09 Trial Exam

Multiple Choice Q3:

3. The molar heat of combustion of ethanol is 1367kJ/mol
What mass of ethanol is required to heat 1.0 moles of water by 10 degrees.

a - 136.7g
b - 46.0g
c - 25.3g
d - 0.025g
 

EazyEEE

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This is from Independent 09 Trial Exam

Multiple Choice Q3:

3. The molar heat of combustion of ethanol is 1367kJ/mol
What mass of ethanol is required to heat 1.0 moles of water by 10 degrees.

a - 136.7g
b - 46.0g
c - 25.3g
d - 0.025g
I think its c

heat needed = mass * 4.22 * temperature to be raised

heat needed = (16.00+2*1.008) * 4.22 * (10) = 760 joules not kilojoules

can someone confirm the bold part?

then, 760/1367 is the moles of ethanol needed.

then mole * molar mass
 

Aesytic

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the bold part is correct i think, but then you have to convert it to kilojoules since the molar heat of combustion is in kilojoules
 

nightweaver066

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I think its c

heat needed = mass * 4.22 * temperature to be raised

heat needed = (16.00+2*1.008) * 4.22 * (10) = 760 joules not kilojoules

can someone confirm the bold part?

then, 760/1367 is the moles of ethanol needed.

then mole * molar mass
1. Heat capacity of water is 4.18J/gC
2. Yes you are correct that it is joules
3. You forgot to convert kilojoules to joules (ethanol molar heat)
 

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