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12.2 Chemical Calculations. By: Rita Akhian Q. 4 technology project Chemistry. Mole Ratio. A mole ratio is a conversion factor derived from the coefficients of a balanced chemical equation interpreted in terms of moles.
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12.2 Chemical Calculations By: Rita Akhian Q. 4 technology project Chemistry
Mole Ratio • A mole ratio is a conversion factor derived from the coefficients of a balanced chemical equation interpreted in terms of moles. • Mole ratios are used to convert between moles of reactants and moles of products. For Example: N₂(g) + 3H₂(g) 2NH₃(g) 1 mol N₂/3 mol H₂ 2 mol NH₃/1 mol N₂ 3 mol H₂/2 mol NH₃
Calculations • In a mole-mole calculation, the unknown can be either a reactant or a product. • In mass-mass calculations, the amount of a substance is determined by measuring its mass in grams. The mass can later be converted to moles by using the molar mass. Then use the molar mass to calculate the number of moles in that mass. • Moles to mass (mass-mass, mass-mole, and mole-mass)
Stoichiometric Calculations • The given quantity is first converted to moles. Then the mole ratio from the balanced equation is used to calculate the number of moles of the wanted substance. The moles are later converted to any other unit of measurement related to the unit mole, in the required problem.
Examples that can be solved with stoichiometric calculations: • The given quantity can be expressed in numbers of representative particles, units of mass, or volume of gases at STP. • Mass-mass • Mass-moles • Mass-volume • Volume-volume • Particle-mass Etc.
Volume-volume example problem: • Practice problem #17 pg 365 The equation for the combustion of carbon monoxide is 2CO(g) + O₂(g) 2CO₂(g). How many liters of oxygen are required to burn 3.86 L of carbon monoxide? 3.86L CO x 1 mol CO x 1 mol O₂ x 22.4L O₂ = 22.4L CO 1 mol CO 1 mol O₂ 3.86 L O₂