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Unformatted text preview: Mass Calculations:
· Relates mass of reactants and products in a balanced chemical equat ion Examples: 1. What mass of oxygen will be required to react completely with 96.1 g of propane, C3H8, according to the equation below? 1 C3H8 (g) + 5 O2 (g) 3 CO2 (g) + 4 H2O (g) 1 mo l C3H8 5 mo l O2 32.0 g O2 96.1 g C3H8 x ¾¾¾¾¾ x ¾¾¾¾¾ x ¾¾¾¾¾ = 349 g O2 44.1 g C3H8 1 mo l C3H8 1 mo l O2 Molar Mass Mole Ratio Molar Mass 2. What mass of carbon dio xide will be produced from the react ion of 175 g of propane, as shown above? 175 g C3H8 x ¾¾¾¾¾¾¾ x ¾¾¾¾¾¾¾ x ¾¾¾¾¾¾¾ = g CO2 23 Chemistry 51 Chapter 6 LIMITING REACTANT
· When 2 or more reactants are combined in nonstoichiometric ratios, the amount of product produced is limited by the reactant that is not in excess.
· This reactant is referred to as limiting reactant.
· When do ing stoichio metric problems o f this type, the limit ing reactant must be determined first before proceeding wit h the calculat ions. Analogy: The number of sundaes possible is limited by the amount of syrup, the limiting reactant.
· When so lving limit ing reactant problems, assume each reactant is limit ing reactant and calculate the desired quantit y based on that assumpt ion.
· Compare your answers for each assumpt ion; the lower value is the correct assumpt ion. 24 Chemistry 51 Chapter 6 LIMITING REACTANT Examples: 1. How many mo les of H2O can be produced by reacting 4.0 mo l of hydrogen and 3.0 mo l of oxygen gases as shown below: 2 H2 (g) + 1 O2 (g) 2 H2O (g) Assume hydrogen is the limit ing reactant: 4.0 mo l H2 x ¾¾¾¾¾¾¾¾ = mol H2O Assume oxygen is the limit ing reactant: 3.0 mo l O2 x ¾¾¾¾¾¾¾¾ = mol H2O Correct limit ing reactant is _________ and __________ mo l of H2O are produced. 25 Chemistry 51 Chapter 6 2. A fuel mixture used in the early days o f rocketry was a mixture of N2H4 and N2O4, as shown below. How many grams of N2 gas is produced when 100 g of N2H4 and 200 g of N2O4 are mixed...
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