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Consider the reaction between 50.0 ml liquid methanol, ch3oh (density 0.850 g/ml), and 22.8 l o2 at 27c and a pressure of 2.00 atm. the products of the reaction are co2(g) and h2o(g). calculate the number of moles of h2o formed if the reaction goes to completion.

Respuesta :

superman1987
The reaction balanced equation is:
2CH3OH + 3O2 → 2CO2 + 4 H2O
the no.of moles of CH3OH = Mass of CH3OH / molar mass of CH3OH
when the mass of CH3OH = volume * density of CH3OH
                                             = 50 * 0.850 = 42.5 g
∴no of moles of CH3OH = 42.5 g / 32 g/mol =1.328 moles
after that to get the no.of moles of the gas O2 we have to decrease the T from 27 °C to zero and the pressure from 2 atm to 1 atm to get the corrected volume to STP.
So by substitution in this formula:
no.of moles of O2 = difference T in Kelvin * volume * change in pressure/molar volume
when we have difference T in kelvin to get V correction = 273K/(27°C+273K)=0.91 K
and Volume in the start = 22.8 L
the change in pressure = 2atm/1atm = 2 atm
and the molar volume = 22.4 L (as according to STP 1 mole of any gas occupies 22.4 L)
So by substitution:
no.ofmoles of O2 = (0.91 * 22.8 * 2) / 22.4 = 1.832 moles 
and according to the balanced equation:
∴ the no.of moles of H2O = no.ofmoles of O2 * (4 mol H2O /3 mol O2)
                                           = 1.832 * (4/3) =2.44 moles