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F4 Chem concentration of soln
發問:
唔明點解個[答案]係咁 可唔可以解俾我聽?1. 4.00 g of sodium hydroxide is dissolved in 500 cm3 of water to make a solution. What is the concentration of the solution? (RAM: H=1.0, O=16.0, Na=23.0)A. 8.00 g dm-3B. 0.200 MC. slightly higher than 0.200 M[D]. slightly lower than 0.200 M2. What is the concentration... 顯示更多 唔明點解個[答案]係咁 可唔可以解俾我聽? 1. 4.00 g of sodium hydroxide is dissolved in 500 cm3 of water to make a solution. What is the concentration of the solution? (RAM: H=1.0, O=16.0, Na=23.0) A. 8.00 g dm-3 B. 0.200 M C. slightly higher than 0.200 M [D]. slightly lower than 0.200 M 2. What is the concentration (in g dm-3) of 0.35 mol dm-3 of potassium sulphate solution? (RAM: O=16.0, S=32.1, K=39.1) A. 41.7 B. 47.3 C. 55.4 [D]. 61.0 更新: "When 4.00 g of sodium hydroxide is dissolved in 500 cm3 of water, the volume ofsolution formed is slightly greater than 500 cm3." 唔明e句 更新 2: sry still dun understand why "體積稍大於 500 cm3"?? thx
1. When 4.00 g of sodium hydroxide is dissolved in 500 cm3 of water, the volume ofsolution formed is slightly greater than 500 cm3. Let (500 + Δv) cm3 be the volume of the solution formed, where Δv is relativelysmall when compared with 500. Molar mass of NaOH = 23.0 + 16.0 + 1.0 = 40.0 g mol?1 No. of moles of NaOH = 4.00/40.0 = 0.100 mol Volume of the solution = (500 + Δv) cm3 = (0.500 + 0.001Δv) dm3 Molarity of the solution = 0.1 / (0.500 + 0.001Δv) < 0.1 / 0.500 = 0.200 M The molarity < 0.200 M, but the difference is small. Hence, D is the answer. ***** 2. Molar mass of K2SO4 = 39.1x2 + 32.1 + 16x4 = 174.3 g mol?1 Mass of 0.35 mol K2SO4 = 174.3 x 0.35 = 61.0 g Molarity of the solution = 0.35 mol dm?3 = 61.0 g dm?3 Hence, D is the answer. 2013-03-28 00:38:17 補充： "When 4.00 g of sodium hydroxide is dissolved in 500 cm3 of water, the volume of the solution formed is slightly greater than 500 cm3." 「當 4.00 g 氫氧化鈉溶於 500 cm3 水中，所形成溶液的體積稍大於 500 cm3。」 2013-03-29 02:24:51 補充： 水原來體積是 500 cm3，全部由水分子組成。 當水溶解了 4.00 g 的氫氧化鈉時，變成氫氧化鈉溶液，溶液中的物質比原來的水多了一些氫氧離子和鈉離子，這些離子佔有一定體積，故此體積會增加，較原來的 500 cm3 大。 但 4.00 g 氫氧化鈉與 500 cm3 (500 g) 水比較，前者的量較後者少得多，而且氫氧離子和鈉離子有部分只佔有水分子間的空隙，故此體積的改變很小，只稍大於原來的 500 cm3。 2013-03-29 02:26:12 補充： 水原來體積是 500 cm3，全部由水分子組成。 當水溶解了 4.00 g 的氫氧化鈉時，變成氫氧化鈉溶液，溶液中的物質比原來的水多了一些氫氧離子和鈉離子，這些離子佔有一定體積，故此體積會增加，較原來的 500 cm3 大。 但 4.00 g 氫氧化鈉與 500 cm3 (500 g) 水比較，前者的量較後者少得多，而且氫氧離子和鈉離子有部分只佔有水分子間的空隙，故此體積的改變很小，只稍大於原來的 500 cm3。
其他解答:6FE1C172A843305D
F4 Chem concentration of soln
發問:
唔明點解個[答案]係咁 可唔可以解俾我聽?1. 4.00 g of sodium hydroxide is dissolved in 500 cm3 of water to make a solution. What is the concentration of the solution? (RAM: H=1.0, O=16.0, Na=23.0)A. 8.00 g dm-3B. 0.200 MC. slightly higher than 0.200 M[D]. slightly lower than 0.200 M2. What is the concentration... 顯示更多 唔明點解個[答案]係咁 可唔可以解俾我聽? 1. 4.00 g of sodium hydroxide is dissolved in 500 cm3 of water to make a solution. What is the concentration of the solution? (RAM: H=1.0, O=16.0, Na=23.0) A. 8.00 g dm-3 B. 0.200 M C. slightly higher than 0.200 M [D]. slightly lower than 0.200 M 2. What is the concentration (in g dm-3) of 0.35 mol dm-3 of potassium sulphate solution? (RAM: O=16.0, S=32.1, K=39.1) A. 41.7 B. 47.3 C. 55.4 [D]. 61.0 更新: "When 4.00 g of sodium hydroxide is dissolved in 500 cm3 of water, the volume ofsolution formed is slightly greater than 500 cm3." 唔明e句 更新 2: sry still dun understand why "體積稍大於 500 cm3"?? thx
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最佳解答:1. When 4.00 g of sodium hydroxide is dissolved in 500 cm3 of water, the volume ofsolution formed is slightly greater than 500 cm3. Let (500 + Δv) cm3 be the volume of the solution formed, where Δv is relativelysmall when compared with 500. Molar mass of NaOH = 23.0 + 16.0 + 1.0 = 40.0 g mol?1 No. of moles of NaOH = 4.00/40.0 = 0.100 mol Volume of the solution = (500 + Δv) cm3 = (0.500 + 0.001Δv) dm3 Molarity of the solution = 0.1 / (0.500 + 0.001Δv) < 0.1 / 0.500 = 0.200 M The molarity < 0.200 M, but the difference is small. Hence, D is the answer. ***** 2. Molar mass of K2SO4 = 39.1x2 + 32.1 + 16x4 = 174.3 g mol?1 Mass of 0.35 mol K2SO4 = 174.3 x 0.35 = 61.0 g Molarity of the solution = 0.35 mol dm?3 = 61.0 g dm?3 Hence, D is the answer. 2013-03-28 00:38:17 補充： "When 4.00 g of sodium hydroxide is dissolved in 500 cm3 of water, the volume of the solution formed is slightly greater than 500 cm3." 「當 4.00 g 氫氧化鈉溶於 500 cm3 水中，所形成溶液的體積稍大於 500 cm3。」 2013-03-29 02:24:51 補充： 水原來體積是 500 cm3，全部由水分子組成。 當水溶解了 4.00 g 的氫氧化鈉時，變成氫氧化鈉溶液，溶液中的物質比原來的水多了一些氫氧離子和鈉離子，這些離子佔有一定體積，故此體積會增加，較原來的 500 cm3 大。 但 4.00 g 氫氧化鈉與 500 cm3 (500 g) 水比較，前者的量較後者少得多，而且氫氧離子和鈉離子有部分只佔有水分子間的空隙，故此體積的改變很小，只稍大於原來的 500 cm3。 2013-03-29 02:26:12 補充： 水原來體積是 500 cm3，全部由水分子組成。 當水溶解了 4.00 g 的氫氧化鈉時，變成氫氧化鈉溶液，溶液中的物質比原來的水多了一些氫氧離子和鈉離子，這些離子佔有一定體積，故此體積會增加，較原來的 500 cm3 大。 但 4.00 g 氫氧化鈉與 500 cm3 (500 g) 水比較，前者的量較後者少得多，而且氫氧離子和鈉離子有部分只佔有水分子間的空隙，故此體積的改變很小，只稍大於原來的 500 cm3。
其他解答:6FE1C172A843305D
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