Ch 3 Stoichiometry and Calculations.pdf

# By just observing this bike no conversion factors can

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By just observing this bike, no conversion factors can be deduced equating the mass of the bike, the bike frame, the wheels and pedals By just observing the bike, we can deduce conversion factors relating the numbers of the components of the bike Scale these relationships up to a collection of parts equal to a Scale these relationships up to a collection of parts equal to a mol 54 S. Ensign, stoichiometry and calculations Empirical formula from experimental analysis 1. Base calculation on 100 grams of compound. 2. Determine moles of each element in 100 grams of compound. 3. Divide each value of moles by the 3. Divide each value of moles by the smallest of the values. 4 Multiply each number by an integer to 4. Multiply each number by an integer to obtain all whole numbers. 55 S. Ensign, stoichiometry and calculations The compound hydrazine (FW = 32) consists f N d H Th t f N d of N and H. The mass percentages of N and H in hydrazine are 87.42% and 12.58%, respecti el respectively. What is the empirical formula for hydrazine? What is the molecular formula for hydrazine? 56 S. Ensign, stoichiometry and calculations

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The compound hydrazine (FW = 32) consists of N and H. The mass percentages of N and H in hydrazine are 87.42% and 12.58%, respectively. What is the empirical formula for hydrazine? What is the molecular formula for hydrazine? 1. Base calculation on 100 grams of compound. 2. Determine moles of each element in 100 grams of compound. 3. Divide each value of moles by the smallest of the values. 4. Multiply each number by an integer to obtain all whole numbers. 57 S. Ensign, stoichiometry and calculations What is the molecular formula for hydrazine? Determine true molar mass of hydrazine experimentally Compare true molar mass to the molar mass based on empirical formula The true molar mass will be the empirical mass multiplied by some number “n” Multiply “n” by the empirical formula to get the molecular formula 58 S. Ensign, stoichiometry and calculations Mothballs are made of napthalene, a C and H containing compound. The mass % of C in naphthalene is 93.71%, while the mass % of H is 6.29%. Naphthalene has a true molar mass of 128 amu. What is the empirical formula for naphthalene? What is the molecular formula for naphthalene? 59 S. Ensign, stoichiometry and calculations Mothballs are made of napthalene, a C and H containing compound. The mass % of C in naphthalene is 93.71%, while the mass % of H is 6.29%. Naphthalene has a true molar mass of 128 amu. What is the empirical formula for naphthalene? What is the molecular formula for naphthalene? 60 S. Ensign, stoichiometry and calculations
Quantitative information from b l d h i l ti balanced chemical equations 2H 2 + O 2 2H 2 O 61 S. Ensign, stoichiometry and calculations Quantitative information from balanced chemical equations 2H 2 + O 2 2H 2 O Stoichiometricall eq i alent q antities are sed Stoichiometrically equivalent quantities are used as conversion factors • Molecules relate to molecules as mols relate to Molecules relate to molecules as mols relate to mols

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