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PERCENT COMPOSITION. used to determine the formula of a compound % by mass of each element in a compound % of element E in a compound: %E = total grams of E MM of compound. PERCENT COMPOSITION.
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PERCENT COMPOSITION used to determine • the formula of a compound • % by mass of each element in a compound % of element E in a compound: %E = total grams of E MM of compound
PERCENT COMPOSITION If 8.20 g of magnesium combines with 5.40 g of oxygen to form a compound, what is the % comp. of this compound? 60.3% Mg, 39.7% O
Calc. % composition of C3H8. 81.68% C, 18.32% H Calc. % comp of each element in sodium bisulfate. 19.15% Na, 0.841% H, 26.71% S, 53.30% O PERCENT COMPOSITION
EMPIRICAL FORMULA • lowest whole-number ratio of atoms of the elements in a cmpd. • ionic: always empirical • molecular: usually not empirical ex: C2H6 empirical formula: CH3
EMPIRICAL FORMULA Calc. the empirical formula of a compound that is 25.9% nitrogen and 74.1% oxygen. N2O5
EMPIRICAL FORMULA steps: • change % to g • convert g to moles • divide each number of moles by the smallest number • determine lowest whole numbers (multiply by common factor)
EMPIRICAL FORMULA Calc. empirical formula of a cmpd that is 52.1% C, 13.2% H and 34.7% O. C2H6O