Question

Okay, so the question on my HW is:
How many moles of H2O* are produced when 64.0 g C2H2* burn in oxygen?
*numbers are supposed to be in subscript
Help?

Answer 1

@zaynahf...?

Answer 2

C2H2 has a molecular weight of 26 so there are 64/26 moles of C2H2.
One mole of H2O can be made from one mole of C2H2; so under the assumption that there is more oxygen than C2H2, moles H2O = moles C2H2

Answer 3

you should approach these questions systematically:
(1) write equation and balance it
C2H2 + O2 -> CO2 + H2O

(2) convert all the values given to moles

moles=mass/molarmass

(3) depending on what they ask for, use the coefficients to find their relationship in terms of ratios

eg. aA + bB -> cC + dD

lower case = coefficient
upper case = element/molecule/whatever

so lets say you know the values of the coefficients (since you balanced the equation) and they gave you a certain amount of moles of A, and you want to find the amount of moles of C produced...

set up a ratio

\[\frac{ moles of A }{ a }=\frac{ moles of C }{ c }\]

species over their respective coefficient, and isolate for what you want

\[moles of C=\frac{ moles of A (c) }{ a }\]