# Define standard heat of formation. Explain why it is important in thermoche?

Then teach the underlying concepts
Don't copy without citing sources
preview
?

#### Explanation

Explain in detail...

#### Explanation:

I want someone to double check my answer

1
Feb 8, 2018

Heat of formation is the change in heat when a compound is formed from its elements. Standard heat of formation is the heat of formation when the synthesis is performed at 298 K and 1 atm

#### Explanation:

Many times we use Hess's Law to determine the change in heat for a reaction that was not measured by adding together reaction equations to produce the desired reaction equation. Standard heats of formation are known for many compounds and can be used this way. For example:

$2 C O \left(g\right) + {O}_{2} \left(g\right) \rightarrow 2 C {O}_{2} \left(g\right)$ $\Delta H = - 566.0 k J$

$C \left(s\right) + {O}_{2} \left(g\right) \rightarrow C {O}_{2} \left(g\right)$ $\Delta H = - 393.5 k J$

If I reverse its direction of the first reaction, the sign of delta H changes, then multiply second reaction by 2 and add it :
$2 C {O}_{2} \left(g\right) \rightarrow 2 C O + {O}_{2} \left(g\right)$ $\Delta H = + 566.0 k J$
$2 C \left(s\right) + 2 {O}_{2} \left(g\right) \rightarrow 2 C {O}_{2} \left(g\right)$ $\Delta H = 2 \left(- 393.5 k J\right) = - 787 k J$
$2 C \left(s\right) + {O}_{2} \left(g\right) \rightarrow 2 C O \left(g\right)$ which must have a Delta H = (566 kJ + (-787 kJ) or -221kJ

• 11 minutes ago
• 12 minutes ago
• 13 minutes ago
• 13 minutes ago
• 2 minutes ago
• 3 minutes ago
• 4 minutes ago
• 5 minutes ago
• 9 minutes ago
• 10 minutes ago
• 11 minutes ago
• 12 minutes ago
• 13 minutes ago
• 13 minutes ago