Determining Chemical Formulas

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Presentation transcript:

Determining Chemical Formulas 7.4

Empirical Formula Empirical Formula – the ________ for the elements combined in a compound, with _________ showing the smallest whole-number mole ratio of the ____________ atoms in the compound.

Calculation Calculate the empirical formula of a substance that is 78.1% B and 21.9 % H. Assume you have _____ grams total. Use molar mass to convert to moles of each. Divide by the smallest # of moles. Round to the nearest whole number.

Calculations In a new alkaline battery, one substance is composed of 63.0% manganese and 37.0% oxygen by mass. Determine the empirical formula of the compound in the battery. To make sure your answer is correct, calculate the % composition of all elements from your answer and compare.

Calculation Determine the empirical formula of a compound that is composed of 60.0% carbon, 13.4% hydrogen, and 26.6% oxygen.

Calculations Find the empirical formula of a compound found to contain 26.56% potassium, 35.41% chromium, and the remainder oxygen.

Molecular Formulas Molecular formula – the actual formula x(empirical. form) = molecular form x is a _________ number Need the _________ ________ and the _________________ mass to determine molecular formula

Calculation Diborane has a mass of 27.67 and an empirical formula of BH3. Determine the molecular formula of diborane. The empirical formula of a compound is found to be P2O5. The molar mass of the compound is 284 g/mol. Determine the molecular formula of the compound.

Calculations Determine the molecular formula of a compounds that has an empirical formula of CH and a molar mass of 78.12 g/mol. Determine the molecular formula of a substance that has an empirical formula of CH2O and a molar mass of 120.12 g/mol.

Calculations Determine the empirical formula of a substance that is 28.253% Iron and 71.747% Chlorine. Determine the empirical formula of a substance that is 76.880% Re and 23.120% O.