Consider the following reaction: 2CH3OH(g)2CH4(g)+O2(g), H =+252.8 kJ Part A Cal

ID: 890957 • Letter: C

Question

Consider the following reaction:

2CH3OH(g)2CH4(g)+O2(g),H=+252.8 kJ

Part A

Calculate the amount of heat transferred when 24.0 g of CH3OH(g) is decomposed by this reaction at constant pressure.

Express the heat to three significant digits with the appropriate units.

Part B

For a given sample of CH3OH, the enthalpy change during the reaction is 82.7 kJ . What mass of methane gas is produced?

Express the mass to three significant digits with the appropriate units.

Part C

How many kilojoules of heat are released when 38.6 g of CH4(g) reacts completely with O2(g)to form CH3OH(g) at constant pressure?

Express heat to three significant digits with the appropriate units.

(EDITED)

24 g of CH3OH

MW of CH3OH = 32.04

moles = mass/MW = 24/32 = 0.75 gmol

note that the reaction is based for 2 mols! so for 0.75 mols

0.75/2 * (252.8 kJ) = 94.8 kJ ---> 94.8 kJ (3 sign.)

H = 82.7 kJ

what mass of methane was there=

So we got form las exercise that 25 g of CH3OH will give 98.8 kJ so..

for 82.7 kJ/ then we get (82.7/98.8)*25 = 20.926 mass of CH3OH were there

BUT!

1 mol of CH3 produces 1 mol of CH4

change 20.926 gof CH3OH to mol

20.926/32 = 0.654 gmol of CH3OH, therefore... we produced 1:! that is 0.654 mol of CH4

if 38.6 g of CH4 + oxygen form CH3OH at P ct

that is

MW CH4 = 16

mol = 38.6/16 = 2.42 gmol of CH4

The reaction

2CH3OH(g)?2CH4(g)+O2(g),?H=+252.8 kJ

may be inverted

2CH4(g)+O2(g)?2CH3OH(g),?H= - 252.8 kJ

If 2 mol of CH4 --->-252.8 kJ

then

2.42 mol of CH4 --> 305.89 kJ or 305 kJ (/3 significant fig)

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