- #1
henry3369
- 194
- 0
Homework Statement
What mass of ethanol, C2H5OH(l), must be burned to supply 1000 kJ of heat? The standard enthalpy of combustion of ethanol at 298 K is -1368 kJ⋅mol-1, and its molecular weight is 46.07 g⋅mol-1 .
I know how to solve this, but I'm unsure about the number of significant figures.
Homework Equations
Solved using dimensional analysis
The Attempt at a Solution
1000 kJ * (1 mol/1368kJ) * (46.07g/1mol) = 33.68 g.
So apparently 4 significant figures is correct, but I don't understand why. Shouldn't be 1 significant figure because 1000 was used in the calculation? My teacher takes off points for incorrect number of significant figures and I would've reported the answer as 30 g in this case. And I did check to make sure that 1000 wasn't followed by a decimal point (1000.)