ETHANOL QUESTION (1 Viewer)

[hscwav2012]

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

 

[Kimyia]

I'm going to say (d).

 

[EazyEEE]

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]

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]

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)