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8a). The formula of a hydrated calcium chloride crystal CaCl2?xH2O. The percentage by mass of the water of crystallization in CaCl2?xH2O is 24.9%. When 52.92g of the crystal is exposed to air for 3 days, the weight increases to 78.84g due to the absorption of water (moisture) in air. The water absorbed is turned... 顯示更多 8a). The formula of a hydrated calcium chloride crystal CaCl2?xH2O. The percentage by mass of the water of crystallization in CaCl2?xH2O is 24.9%. When 52.92g of the crystal is exposed to air for 3 days, the weight increases to 78.84g due to the absorption of water (moisture) in air. The water absorbed is turned into water of crystallization of the crystal. i). Calculate the value of x. ii). Calculate the number of moles of water absorbed by 1 mole of CaCl2?xH2O after 3 days.
最佳解答:
The formula of a hydrated calcium chloride crystal CaCl-2-?xH-2O. The percentage by mass of the water of crystallization in CaCl-2-?xH-2O is 24.9%. When 52.92g of the crystal is exposed to air for 3 days, the weight increases to 78.84g due to the absorption of water (moisture) in air. The water absorbed is turned into water of crystallization of the crystal. i). Calculate the value of x. Molar mass of CaCl-2- = 40.1 + 35.5 X 2 = 111.1 gmol-1-- Mass of CaCl-2- in the crystal = 52.92 X (1 – 24.9%) = 39.74 g -So, no. of mole of CaCl-2- = mass / molar mass = 39.74 / 111.1 = 0.3577 mol Mass of water in the crystal = 52.92 – 39.74 = 13.18 g Molar mass of water, H-2-O = 1.0 X 2 + 16.0 = 18.0 gmol---1 So, no. of mole of H-2-O = mass / molar mass = 13.18 / 18.0 = 0.732 mol Therefore, mole ratio of CaCl-2- : H-2-O = 0.3577 : 0.732 = 1 : 2 So, in one mole of CaCl-2-, there are 2 moles of H-2-O So, x = 2 ii. Calculate the number of moles of water absorbed by 1 mole of CaCl2?xH2O after 3 days. Molar mass of CaCl-2-?xH-2O = 111.1 + 2(18.0) = 147.1 gmol---1- - So, number of mole of CaCl-2-?xH-2O = mass / molar mass = 52.92 / 147.1 = 0.3598 mol Mass of water absorbed = 78.84 – 52.92 = 25.92 g So, no. of mole of water absorbed = mass / molar mass = 25.92 / 18.0 = 1.44 mol So, molar ratio of CaCl-2-?xH-2O : H-2O = 0.3598 : 1.44 = 1 : 4 So, for one mole of the crystal, it will absorb 4 moles of water.
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唔識呀!!!!Chem呀!!!有冇人幫我呀!!!!!!唔識計formula同no. of mole呀!!!!!!!發問:
8a). The formula of a hydrated calcium chloride crystal CaCl2?xH2O. The percentage by mass of the water of crystallization in CaCl2?xH2O is 24.9%. When 52.92g of the crystal is exposed to air for 3 days, the weight increases to 78.84g due to the absorption of water (moisture) in air. The water absorbed is turned... 顯示更多 8a). The formula of a hydrated calcium chloride crystal CaCl2?xH2O. The percentage by mass of the water of crystallization in CaCl2?xH2O is 24.9%. When 52.92g of the crystal is exposed to air for 3 days, the weight increases to 78.84g due to the absorption of water (moisture) in air. The water absorbed is turned into water of crystallization of the crystal. i). Calculate the value of x. ii). Calculate the number of moles of water absorbed by 1 mole of CaCl2?xH2O after 3 days.
最佳解答:
The formula of a hydrated calcium chloride crystal CaCl-2-?xH-2O. The percentage by mass of the water of crystallization in CaCl-2-?xH-2O is 24.9%. When 52.92g of the crystal is exposed to air for 3 days, the weight increases to 78.84g due to the absorption of water (moisture) in air. The water absorbed is turned into water of crystallization of the crystal. i). Calculate the value of x. Molar mass of CaCl-2- = 40.1 + 35.5 X 2 = 111.1 gmol-1-- Mass of CaCl-2- in the crystal = 52.92 X (1 – 24.9%) = 39.74 g -So, no. of mole of CaCl-2- = mass / molar mass = 39.74 / 111.1 = 0.3577 mol Mass of water in the crystal = 52.92 – 39.74 = 13.18 g Molar mass of water, H-2-O = 1.0 X 2 + 16.0 = 18.0 gmol---1 So, no. of mole of H-2-O = mass / molar mass = 13.18 / 18.0 = 0.732 mol Therefore, mole ratio of CaCl-2- : H-2-O = 0.3577 : 0.732 = 1 : 2 So, in one mole of CaCl-2-, there are 2 moles of H-2-O So, x = 2 ii. Calculate the number of moles of water absorbed by 1 mole of CaCl2?xH2O after 3 days. Molar mass of CaCl-2-?xH-2O = 111.1 + 2(18.0) = 147.1 gmol---1- - So, number of mole of CaCl-2-?xH-2O = mass / molar mass = 52.92 / 147.1 = 0.3598 mol Mass of water absorbed = 78.84 – 52.92 = 25.92 g So, no. of mole of water absorbed = mass / molar mass = 25.92 / 18.0 = 1.44 mol So, molar ratio of CaCl-2-?xH-2O : H-2O = 0.3598 : 1.44 = 1 : 4 So, for one mole of the crystal, it will absorb 4 moles of water.
其他解答:
你問咩?請用中文。thx
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