This physics problem tests your understanding of fundamental physical laws and their applications. The step-by-step solution below breaks down the problem using relevant equations and physical reasoning.
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Okay, Gezahagn, let's continue with these questions. 20. A quantity of gas has a volume of 25 L at 17 °C and 3 atm of pressure. To what volume must the gas be increased for a gas to be under STP conditions? Step 1: Identify the given values and the law to use. This is a Combined Gas Law problem: (P_1V_1)/(T_1) = (P_2V_2)/(T_2). Temperatures must be in Kelvin. STP conditions are P_2 = 1 atm and T_2 = 0 °C = 273.15 K. Given: P_1 = 3 atm V_1 = 25 L T_1 = 17 °C = 17 + 273.15 = 290.15 K P_2 = 1 atm (STP) T_2 = 0 °C = 273.15 K V_2 = ? Step 2: Rearrange the formula to solve for V_2. V_2 = (P_1V_1T_2)/(P_2T_1) Step 3: Substitute the values and calculate V_2. V_2 = (3 atm)(25 L)(273.15 K)(1 atm)(290.15 K) V_2 = 20486.25 L290.15 V_2 ≈ 70.606 L Step 4: Compare with the given options. The closest option is c. 70.60 L. The final answer is c. 70.60 L 21. What is the molecular weight of a pure gaseous compound having a density of 4.95 g/L at -35 °C and 1020 torr? Step 1: Identify the given values and the appropriate formula. We use the Ideal Gas Law in terms of density: PM = RT, where M is the molecular weight. Given: Density () = 4.95 g/L Temperature (T) = -35 °C = -35 + 273.15 = 238.15 K Pressure (P) = 1020 torr Gas constant (R) = 62.36 L torr/(mol K) (since pressure is in torr) Step 2: Rearrange the formula to solve for M. M = ( RT)/(P) Step 3: Substitute the values and calculate M. M = (4.95 g/L)(62.36 L torr/(mol K))(238.15 K)1020 torr M = (73504.698)/(1020) g/mol M ≈ 72.06 g/mol Step 4: Compare with the given options. The closest option is b. 72 g/mol. The final answer is b. 72 g/mol 22. If helium (He) diffuses through a porous barrier at a rate of 4.0 moles per minute, at what rate (in moles per minute) would oxygen (O₂) gas diffuse? Step 1: Identify the given values and the appropriate law. We use Graham's Law of Diffusion: (r_1)/(r_2) = sqrt((M_2)/(M_1)). Given: Rate of He (r_He) = 4.0 mol/min Molar mass of He (M_He) = 4.00 g/mol Molar mass of O₂ (M_O_2) = 2 × 16.00 = 32.00 g/mol We need to find the rate of O₂ (r_O_2). Step 2: Set up Graham's Law equation. r_Her_O_2 = sqrt(M_O_2)M_He Step 3: Substitute the values and solve for r_O_2. 4.0 mol/minr_O_2 = sqrt(32.00 g/mol)4.00 g/mol (4.0)/(r_O_2) = sqrt(8) (4.0)/(r_O_2) ≈ 2.828 r_O_2 = (4.0)/(2.828) mol/min r_O_2 ≈ 1.414 mol/min Step 4: Compare with the given options. The closest option is a. 1.4. The final answer is a. 1.4 23. What will happen water when freezes? The correct answer is b. Water changes from a liquid to a solid state. Freezing is the phase transition of a substance from a liquid to a solid state. 24. What is sublimation? The correct answer is a. When a solid turns into a gas. Sublimation is the process where a substance changes directly from a solid to a gas without passing through the liquid phase. 25. What eventually happens if energy is continually removed from a liquid? The correct answer is b. It freezes. Removing energy from a liquid causes its temperature to decrease. If enough energy is removed, the liquid will undergo a phase transition to a solid state, which is called freezing. 3 done, 2 left today. You're making progress.