c. Water changes from a solid to a gas state
d. Water changes from a gas to a plasma state
24. What is sublimation?
a. When a solid turns into a gas
b. When a gas tums into a liquid
c. When a gas turns into a solid
d. When a solid turns into plasma
25. What eventually happens if energy is continually removed from a liquid?
a. It boils
c. It evaporates
b. It freezes
d. It condenses
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CHEMISTRY GRADE 11
Part IV: Solve the following problems
26. What will be the minimum pressure required to compress \( 500 \mathrm{dm}^{3} \) of air at 1 bar to \( 200 \mathrm{dm}^{3} \) at \( 30^{\circ} \mathrm{C} \) ?
27. A vessel of \( 120 \mathrm{~mL} \). capacity contains a certain amount of gas at \( 35^{\circ} \mathrm{C} \) and 1.2 bar pressure. The gas is transferred to another vessel of volume \( 180 \mathrm{~mL} \) at \( 35^{\circ} \mathrm{C} \) What would be its pressure?
28. Using the ideal gas equation (i.e., \( p V=n R T \) ), show that at a given temperature density of a gas is proportional to gas pressure \( p \).
29. \( 34.05 \mathrm{~mL} \) of phosphorus vapor weighs \( 0.0625 \mathrm{~g} \) at \( 546{ }^{\circ} \mathrm{C} \) and 0.1 bar pressure What is the molar mass of phosphorus?
30. If 0.500 mole of nitrogen gas occupies a volume of \( 11.2 \mathrm{~L} \) at \( 0^{\circ} \mathrm{C} \); what volume will 2.00 mole of nitrogen gas occupy at the same temperature and pressure?
31. What mass of helium in grams is required to fill \( 15.0 \mathrm{~L} \) balloon to a pressure of \( 1.1 \mathrm{~atm} \) at \( 25^{\circ} \mathrm{C} \) ?
32. A sample of a certain gas has a volume of \( 1.25 \mathrm{~L} \) at \( -125 \mathrm{~s}^{\circ} \mathrm{C} \) and \( 5.0 \mathrm{~atm} \). The gas is compressed at \( 50.0 \mathrm{~atm} \) to a volume of \( 325 \mathrm{~mL} \). What is the final temperature of the helium gas in \( { }^{\circ} \mathrm{C} \) ?
33. If \( 140 \mathrm{~cm}^{3} \) of methane diffuse into air in 72 seconds, how long will it take 210 \( \mathrm{cm}^{\prime} \) of sulphur dioxide to diffuse under the same conditions?
34. The temperature of \( 2.5 \mathrm{~L} \) of a gas initially at STP is raised to \( 250^{\circ} \mathrm{C} \) at constant volume; calculate the final pressure of the gas in atmosphere.
35. What total gas volume at \( 520^{\circ} \mathrm{C} \) and 880 tort would result from the decomposition of \( 33 \mathrm{~g} \) of potassium bicarbonate according to the equation:
\[
2 \mathrm{KHCO}_{3}(\mathrm{~s}) \rightarrow \mathrm{K}_{2} \mathrm{CO}_{3}(\mathrm{~g})+\mathrm{H}_{2} \mathrm{O}(\mathrm{g})
\]
