How are diamonds made?
Natural diamonds are mined from sites around the world. However, the price of natural diamonds is carefully controlled, so other sources for diamonds are being explored. Several different methods for producing synthetic diamonds are available, usually involving treating carbon at very high temperatures and pressures. The diamonds produced are now of high quality, but are primarily used in industrial applications. Diamonds are one of the hardest materials available and are widely used for cutting and grinding tools.
Calculating Heat of Reaction from Heat of Formation
Standard Heats of Formation of Selected Substances
|C (s, graphite)
|C (s, diamond)
Sample Problem: Calculating Standard Heat of Reaction
Step 1: List the known quantities and plan the problem.
- ΔHf∘ for NO(g)=90.4 kJ/mol
- ΔHf∘ for O2(g)=0 (element)
- ΔHf∘ for NO2(g)=33.85 kJ/mol
First write the balanced equation for the reaction. Then apply the equation to calculate the standard heat of reaction for the standard heats of formation.
Step 2: Solve.
Applying the equation form the text:
The standard heat of reaction is -113 kJ.
Step 3: Think about your result.
The reaction is exothermic, which makes sense because it is a combustion reaction and combustion reactions always release heat.
- Standard heats of reaction can be calculated from standard heats of formation.
- Is a Hess’s Law calculation a direct determination of a standard heat of reaction?
- What is the purpose of the n in the equation?
- What does ∑ stand for?