Z = 1.134 mol (this is how much oxygen is present)Ĥ7.3 g − (8.78 + 18.144) = 20.376 g (grams of X present in the sample) Y = 0.42525 mol (this is how many moles of X are present in the compound) Mass of just PO 4 in compound -> (94.971 x 2) g = 189.9 g Solution: 64.8 − 48 = 16.8 g (the mass of X in the sample)Ĥ8.0 g / 16.0 g/mol = 3.00 mol of O in sample. What is the molar mass of element X? What is the identity of element X? Therefore, moles M in the sample:Įxample #8: The 64.8 g sample of the compound X 2O 5 contains 48.0 grams of oxygen atoms. Determine the atomic weight of element M and identify it by name. A 1.603 g sample of the compound is found to contain 0.03606 mol of Cl. What is the atomic weight of element X? What element is element X?Įxample #7: The chloride of an unknown metal is believed to have the formula MCl 3. What is the relative atomic mass of X? What is the element X?įrom X 2O, the molar ratio of X to O is 2 to 1Įxample #6: A 64.8 g sample of the compound X 2O 5 contains 48.0 g of oxygen atoms. What are the values of x and y?Īlthough not asked for, the formula is OsO 4Įxample #5: 7.8 g of an element X reacts with oxygen to form 9.4 g of an oxide X 2O. Identify element A.Įxample #4: A 2.89 g sample of osmium oxide, Os xO y, contains 2.16 g of osmium. 0.5386 g of element A is treated with oxygen and 0.711 g of A 2O 3 are formed. Calculate the atomic weight of the element M and identify the metal.ġ) Determine grams, then moles of oxygen:Įxample #3: When the element A is burned in an excess of oxygen, the oxide A 2O 3(s) is formed.
This means that its atomic weight is 58.85 g/mol, the atomic weight of cobalt.Įxample #2: A 1.443 g sample of an unknown metal is reacted with excess oxygen to yield 1.683 grams of an oxide known to have the formula M 2O 3.
Knowing that 57 g are made by fluorine, the unknown atom will count for 58.85 g in each mole. One mole of unknown compound weighs (57/0.492) = 115.85 g. In the molecule of your unknown compound you have three atoms of fluorine, this means that in one mole of this compound you have 57 g of fluorine (from 19.0 x 3) that represent 49.2% by weight. Solution #2: 49.2% by weight of your compound is fluorine. ChemTeam: Determine identity of an element from a binary formula and mass dataĭetermine identity of an element from a binary formula and mass dataĭetermine identity of an element from a binary formula and mass data: questions onlyĬalculate empirical formula when given mass dataĬalculate empirical formula when given percent composition dataĭetermine identity of an element from a binary formula and a percent compositionĮxample #1: 100.0 g of XF 3 contains 49.2 g of fluorine.
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