Answer:
Explanation:
A foam coffe cup is considered a perfectly insulated system: heat energy is not exchanged with the surroundings.
Under that assumption, the heat released by the chemical reaction is equal to the heat absorbed by the system.
1. Heat absorbed by the system:
Use the equation Heat = Q = m × C × ΔT, with:
- m = 126 g (the amount of solution produced)
- C = specific heat of pure water = 4.186 J/gºC
- ΔT = increase of temperature = 24.70 ºC - 21.00ºC = 3.70ºC
Q = 126g × 4.186J/gºC × 3.70ºC = 1,951.5J
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<em><u>2. Enthalpy of the reaction</u></em>
The enthalpy must be reported in kJ/mol.
Then, convert juoles to kilojoules, dividing by 1,000; and divide by 2.00 moles, which is the amount of compound that reacted:
- ΔHrxn = 1,951.5J × (1kJ / 1,000J) × (1 / 2mol) ≈ 0.9758 kJ/mol
Round to <em>3 significant figures</em>: 0.976 kJ/mol
Explanation:
We leave a soda in the car overnight and the temperature dips to 25 °F. To see if it will freeze we have to convert the °F to °C.
T(°C) = ( T(°F) - 32 ) *5/9
T(°C) = (25 - 32) *5/9
T(°C) = -3.9 °C
Since -3.9 °C is a temperature greater than the freezing point (-4.5 °C) the soda won't freeze.
Answer: The soda won't freeze.
