41.9k views
3 votes
Dimethyl ether, a useful organic solvent, is prepared in two steps. In the first step, carbon dioxide and hydrogen react to form methanol and water: CO₂(g) + 3H₂(g)
\rightarrow CH₃OH (l) + H₂O(l); ΔH = -131.kJ In the second step, methanol reacts to form dimethyl ether and water: 2CH₃OH (l)
\rightarrow CH₃OCH₃(g) + H₂O (l); ΔH = 8.kJCalculate the net change in enthalpy for the formation of one mole of dimethyl ether from carbon dioxide and hydrogen from these reactions.Round your answer to the nearest kj.

User Pglezen
by
8.7k points

1 Answer

3 votes

Answer:

ΔH = - 254 kJ

Step-by-step explanation:

The final equation for the enthalpy of formation we want to calculate is:

2 CO₂ (g) + 6 H₂(g) -------------- CH₃OCH₃ (l) ΔH = ?

Notice that if we take the 2 times the first reaction and add the second , by Hess's law we will add the enthalpy changes to obtain our desired ΔH .

( CO₂(g) + 3H₂(g) CH₃OH (l) + H₂O(l); ΔH = -131.kJ) x 2

2CO₂(g) + 6H₂(g) --------- 2CH₃OH (l) + 2 H₂O(l); ΔH = -262.kJ

2CH₃OH (l) --------- CH₃OCH₃(g) + H₂O (l); ΔH = 8.kJ

_____________________________________________________

2CO₂(g) + 6H₂(g) ----------- CH₃OCH₃(g) + 3H₂O (l); ΔH = -254 kJ

User Tigran Sarkisian
by
7.7k points

No related questions found