Problem 22
The enthalpy change for a reaction is a state function and it is an extensive property. Explain.
Problem 23
Standard enthalpies of formation are relative values. What are \(\Delta H_{\mathrm{f}}^{\circ}\) values relative to?
Problem 25
Why is it a good idea to rinse your thermos bottle with hot water before filling it with hot coffee?
Problem 26
Photosynthetic plants use the following reaction to produce glucose, cellulose, and so forth: $$6 \mathrm{CO}_{2}(g)+6 \mathrm{H}_{2} \mathrm{O}(l) \frac{\text { Sunlight }}{\longrightarrow} \mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}(s)+6 \mathrm{O}_{2}(g)$$ How might extensive destruction of forests exacerbate the greenhouse effect?
Problem 27
What is incomplete combustion of fossil fuels? Why can this be a problem?
Problem 28
Explain the advantages and disadvantages of hydrogen as an alternative fuel.
Problem 30
Which has the greater kinetic energy, an object with a mass of 2.0 \(\mathrm{kg}\) and a velocity of 1.0 \(\mathrm{m} / \mathrm{s}\) or an object with a mass of 1.0 \(\mathrm{kg}\) and a velocity of 2.0 \(\mathrm{m} / \mathrm{s}\) ?
Problem 33
A gas absorbs 45 kJ of heat and does 29 kJ of work. Calculate \(\Delta E .\)
Problem 34
Calculate \(\Delta E\) for each of the following. a. \(q=-47 \mathrm{kJ}, w=+88 \mathrm{kJ}\) b. \(q=+82 \mathrm{kJ}, w=-47 \mathrm{kJ}\) c. \(q=+47 \mathrm{kJ}, w=0\) d. In which of these cases do the surroundings do work on the system?
Problem 35
A system undergoes a process consisting of the following two steps: Step 1: The system absorbs 72 \(\mathrm{J}\) of heat while 35 \(\mathrm{J}\) of work is done on it. Step \(2 :\) The system absorbs 35 \(\mathrm{J}\) of heat while performing 72 \(\mathrm{J}\) of work. Calculate \(\Delta E\) for the overall process.
