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about F4 chem mole concept

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有幾條chem 的mole concept題目 唔識做希望各位解答1.What mass of iron is obtained when 0.20 mol of iron(III) oxide are completely reduced by carbon?answer is 11.2 g 2.The following equation represents the reaction of an oxide of iron with hydrogen:Fe3O4(s) + 4H2(g)--->3Fe(s) + 4H2O(l)What mass of iron would be... 顯示更多 有幾條chem 的mole concept題目 唔識做 希望各位解答 1.What mass of iron is obtained when 0.20 mol of iron(III) oxide are completely reduced by carbon? answer is 11.2 g 2.The following equation represents the reaction of an oxide of iron with hydrogen: Fe3O4(s) + 4H2(g)--->3Fe(s) + 4H2O(l) What mass of iron would be obtained if 2.32 g of the oxide was used up in the reaction? (Relative atomic masses: Fe=56, O=16) answer is 1.68g 3. 2.4 g of oxygen contains x atoms at room conditions. How many atoms are present in 12 g of helium? answer is 20x 4.If 1 mole of YO3 contains the same number of atoms as 72 g of YH4, what is the relative atomic mass of Y? answer is 86

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1. Molar mass of Fe = 56 g mol-1 2Fe2O3 + 3C → 4Fe + 3CO2 Mole ratio Fe2O3 : Fe = 2 : 4 = 1 : 2 No. of moles of Fe2O3 used = 0.2 mol No. of moles of Fe formed = 0.2 x 2 = 0.4 mol Mass of Fe formed = mol x (molar mass) = 0.4 x 56 = 22.4 g (The given answer 11.2 g is incorrect.) (If 0.10 mol of iron(III) oxide is used instead, the answer is 11.2 g.) ===== 2. Molar mass of Fe = 56 g mol-1 Molar mass of Fe3O4 = 56x3 + 16x4 = 232 g mol-1 Fe3O4 + 4H2 → 3Fe + 4H2O Mole ratio Fe3O4 : Fe = 1 : 3 No. of moles of Fe3O4 used = mass/(molar mass) = 2.32/232 = 0.01 mol No. of moles of Fe formed = 0.01 x 3 = 0.03 mol Mass of Fe formed = mol x (molar mass) = 0.03 x 56 = 1.68 g ===== 3. Molar mass of O atoms = 16 g mol-1 Molar mass of He atoms = 4 g mol-1 Avogadro number = L No. of moles of O atoms = mass/(molar mass) = 2.4/16 = 0.15 mol No. of O atoms = 0.15L Hence, 0.15L = x L = x/0.15 No. of moles of He atoms = mass/(molar mass) = 12/4 = 3 mol No. of He atoms = 3L = 3(x/0.15) = 20x ===== 4. Let M the relative atomic mass of Y. Thus, molar mass of YH4 = (M + 4) g mol-1 Avogadro number = L In 1 mol of YO3: Each mol of YO3 contains 4 mol of atoms. No. of moles of atoms = 4 mol No. of atoms = 4L atoms In 72 g of YH4: No. of moles of YH4 = [72/(M + 4)] mol Each moles of YH4 contains 5 mol of atoms. No. of moles of atoms = 5[72/(M + 4)] = [360/(M + 4)] mol No. of atoms = [360/(M + 4)]L = [360L/(M + 4)] atoms Given that: 360L/(M + 4) = 4L 4(M + 4) = 360 M + 4 = 90 M = 86 The relative atomic mass of Y is 86. =

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