標題:

Chemistry mass

發問:

1.The oxide of an element with formular X2O5 contains 34.78% oxygen by mass. Find the atomic mass of X.2.A compound has formula MSO4.XH2O. 14.35g of the compound is heated until all the of crystallisation is removed. The mass remaining is 8.05g. Calculatea)the percentage by mass of water of... 顯示更多 1.The oxide of an element with formular X2O5 contains 34.78% oxygen by mass. Find the atomic mass of X. 2.A compound has formula MSO4.XH2O. 14.35g of the compound is heated until all the of crystallisation is removed. The mass remaining is 8.05g. Calculate a)the percentage by mass of water of crystallisation, b)the atomic mass of M and the value of X.(Given that:the formular mass of MSO4 is 161)

最佳解答:

1. Let M be the atomic mass of X. Percentage by mass of O in X2O5 : (16*5)/(2M + 16*5) = 34.78% 80/(2M + 80) = 0.3478 0.6956M + 27.824 = 80 M = 75.01 The atomic mass of X = 75.01 ===== 2. a) The percentage by mass of water of crystallization = [(14.35 - 8.05)/14.35] * 100% = 43.9% b) The atomic mass of M = 161 - (32 + 16*4) = 65 The value of X = 161 * [(14.35 - 8.05)/8.05] / (1*2 + 16) = 7

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