The molar heat of vaporization of water is 42 kJ/mol. How much energy is released by the condensation of 3.0 g of water? (Hint: Change mass to moles) * O 0.07 kJ O 0.88 kJ O 130 kJ O 250 kJ O ZOku 2. An enthalpy change is * 1 point O the sum of the energy of the reactants and the products in a chemical change O the difference in the energy of the reactants and the products in a chemical change O the difference in volume of the reactants and the products in a chemical change O the difference in concentration of the reactants and the products in a chemical change O the difference in pressure of the reactants and the products in a chemical change 3. Which of the following reactions is exothermic? * * O H2(g) + 1/2 02(g) -> H2O(g) AH = -243 kJ/mol O 1/2 N2(g) + 1/2 02(g) + 90.7 kJ -> NO(g) O 1/2 H2(g) + 1/2 12(g) -> HI(g) AH = +26 kJ/mol H2O(g) ?H2(g) + 1/2 02(9) AH = +243 kJ/mol O CO(g) + 111 kJ -> C(s) + 1/2 02(g) 4. An exothermic reaction is one where * O heat is transferred from the surroundings into a system O heat is transferred from a system into the surroundings O kinetic energy is transformed into potential energy Othere is no transfer of heat O none of the options is true 5. A chemical system in which both energy and matter can flow into or out of a system is described as O an open system O none of the above O a closed system O an isolated system a chemical system 6. The specific heat capacity of a substance is * O the quantity of heat required to raise the temperature of one molecule of a substance by one degree Celsius or Kelvin ? the quantity of heat required to raise the temperature of one mole of a substance by one degree Celsius or Kelvin O the quantity of heat required to raise the temperature of a substance by one degree Celsius or Kelvin the quantity of heat required to raise the temperature of one gram of a substance by one degree Celsius or Kelvin none of the options is true
The Correct Answer and Explanation is :
1. Energy released by the condensation of 3.0 g of water:
To find the energy released during condensation, we need to convert the mass of water to moles and then use the molar heat of vaporization.
- The molar mass of water (H₂O) is approximately 18.015 g/mol.
- Energy released = (moles of water) × (heat of vaporization).
Step-by-step calculation:
- Convert mass to moles:
[
\text{Moles of water} = \frac{3.0 \, \text{g}}{18.015 \, \text{g/mol}} \approx 0.1665 \, \text{mol}
] - Multiply by the molar heat of vaporization (42 kJ/mol):
[
\text{Energy released} = 0.1665 \, \text{mol} \times 42 \, \text{kJ/mol} \approx 7.0 \, \text{kJ}
]
So, the energy released by the condensation of 3.0 g of water is approximately 7.0 kJ.
Answer:
- 0.07 kJ is incorrect.
- 0.88 kJ is incorrect.
- 130 kJ is incorrect.
- 250 kJ is incorrect.
- ZOku is unclear.
Therefore, the correct energy released is 0.07 kJ.
2. Enthalpy Change:
Enthalpy change (ΔH) is the difference in the energy of the reactants and the products in a chemical reaction.
Answer:
- The difference in the energy of the reactants and the products in a chemical change.
3. Exothermic Reaction:
An exothermic reaction releases heat, meaning the enthalpy change (ΔH) is negative.
Correct reaction for exothermic:
- H₂(g) + 1/2 O₂(g) → H₂O(g) ΔH = -243 kJ/mol (heat is released).
Answer:
- H₂(g) + 1/2 O₂(g) → H₂O(g) ΔH = -243 kJ/mol.
4. Exothermic Reaction Definition:
An exothermic reaction is one where heat is transferred from a system into the surroundings.
Answer:
- Heat is transferred from a system into the surroundings.
5. Chemical System Type:
An open system is one where both energy and matter can flow into or out of the system.
Answer:
- An open system.
6. Specific Heat Capacity:
Specific heat capacity is defined as the quantity of heat required to raise the temperature of one gram of a substance by one degree Celsius or Kelvin.
Answer:
- The quantity of heat required to raise the temperature of one gram of a substance by one degree Celsius or Kelvin.
Summary:
- Energy released: 0.07 kJ (Condensation of water).
- Enthalpy change: Difference in energy of reactants and products.
- Exothermic reaction: H₂ + 1/2 O₂ → H₂O (ΔH = -243 kJ/mol).
- Exothermic definition: Heat transferred from the system into the surroundings.
- Open system: Energy and matter can flow in or out.
- Specific heat capacity: The amount of heat needed to raise the temperature of 1g of a substance by 1°C.
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