標題:
問CHEM 2004 MC Q.3 AND Q.5
發問:
問CHEM 2004 MC Q.3 AND Q.5 可唔可以解釋下個答案問黎?
3. Chemical formula of water is H2O So, in one water molecule, there are two hydrogen atoms and one oxygen atom. Molar mass of water = 1.0 X 2 + 16.0 = 18.0 g/mol So, no. of mole of water = mass / molar mass = 36.0 / 18.0 = 2.0 mol So, there are 4 moles of hydrogen atoms. So, A is the answer. For B, there are 6.0 mol of atoms. So, there are = 6.0 X 6.02 X 10^23 atoms. For C, there are two mol of molecules. So, there are = 2.0 X 6.02 X 10^23 molecules For D, in the question, molar volume of gas is given. However, it is invalid for liquid (water). The volume of water is much smaller than 48 dm^3. 5. The answer is C. For A, it is nitrate can be used as a fertilizer. Nitric acid is too acidic and corrosive to be a fertilizer. For B, Nitric acid is made from ammonia, not nitrogen monoxide. (Out of syllabus.) For C, it is true that conc. nitric acid will decompose under sunlight. So it has to be stored under brown bottles. 4HNO3 (l) → 4NO2 (g) + 2H2O (l) + O2 (g) For D, the label is explosive, which is not true for nitric acid. The label should be corrosive.
其他解答:
問CHEM 2004 MC Q.3 AND Q.5
發問:
問CHEM 2004 MC Q.3 AND Q.5 可唔可以解釋下個答案問黎?
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最佳解答:3. Chemical formula of water is H2O So, in one water molecule, there are two hydrogen atoms and one oxygen atom. Molar mass of water = 1.0 X 2 + 16.0 = 18.0 g/mol So, no. of mole of water = mass / molar mass = 36.0 / 18.0 = 2.0 mol So, there are 4 moles of hydrogen atoms. So, A is the answer. For B, there are 6.0 mol of atoms. So, there are = 6.0 X 6.02 X 10^23 atoms. For C, there are two mol of molecules. So, there are = 2.0 X 6.02 X 10^23 molecules For D, in the question, molar volume of gas is given. However, it is invalid for liquid (water). The volume of water is much smaller than 48 dm^3. 5. The answer is C. For A, it is nitrate can be used as a fertilizer. Nitric acid is too acidic and corrosive to be a fertilizer. For B, Nitric acid is made from ammonia, not nitrogen monoxide. (Out of syllabus.) For C, it is true that conc. nitric acid will decompose under sunlight. So it has to be stored under brown bottles. 4HNO3 (l) → 4NO2 (g) + 2H2O (l) + O2 (g) For D, the label is explosive, which is not true for nitric acid. The label should be corrosive.
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