A student investigates the temperature changes during three different chemical reactions, P, Q, and R.
Complete the table below by calculating the temperature change for each reaction mixture. Make sure to include a +++ or −-− sign where appropriate.
| Reaction mixture | Temperature at start (°C) | Temperature at end (°C) | Temperature change (°C) |
|---|---|---|---|
| P | 21.0 | 28.5 | ……………\dots\dots\dots\dots\dots…………… |
| Q | 22.5 | 14.5 | ……………\dots\dots\dots\dots\dots…………… |
| R | 18.5 | 18.5 | ……………\dots\dots\dots\dots\dots…………… |
Which reaction mixture represents an exothermic reaction? Explain your answer.
The combustion (burning) of propane gas, C3H8\text{C}_3\text{H}_8C3H8, is an exothermic reaction. When propane burns completely in oxygen, O2\text{O}_2O2, it produces carbon dioxide, CO2\text{CO}_2CO2, and water, H2O\text{H}_2\text{O}H2O.
Write the balanced symbol equation for this reaction.