1. If a certain volume of potassium hydroxide solution with a solute mass percentage of 14% is evaporated to remove 50 g of water, the solute mass fraction becomes 28% and the volume of the solution becomes 62.5 mL. What is the concentration of the substance in the concentrated solution? (A)2.20 M (B)3.00 M (C)4.00 M (D)5.00 M (E)6.25 M

1. If a certain volume of potassium hydroxide solution with a solute mass percentage of 14% is evaporated to remove 50 g of water, the solute mass fraction becomes 28% and the volume of the solution becomes 62.5 mL. What is the concentration of the substance in the concentrated solution?
(A)2.20 M
(B)3.00 M
(C)4.00 M
(D)5.00 M
(E)6.25 M

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統計： A(0), B(1), C(4), D(0), E(2) #3091919

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B1 · 2023/11/29

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55. As shown in the figure below, an RC circuit consists of a resistor R, and two capacitors C1 and C2 with ditterent capacitance). At t =0, the charges stored on C1 and C2 are Q0 and 0, respectively. And the switch is also closed at t = 0. Which of the following statements is true(A)The charges would go back and forth between C1 and C2 repeatedly. (B)The charge would flow back and forth between C1 and C2, but the amount of charge is getting less and less. (C)When one waits long enough, both capacitors share the same amount of energy. (D)When one waits long enough, the voltage across the resistor becomes zero. (E) When one waits long enough, the charges are neutralized and both the positive and negative charges of the two capacitors are zero.

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