| AP Chemistry - Semester 1 : Stoichiometry of Formulas and Equations |
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Sections: Introduction
| Section 1
| Section 2
| Section 3
|  Lab
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3.4 Calculating Amounts of Reactant and Product In a balanced reaction the number of moles of one substance is stoichiometrically equivalent to the number of moles of any other substance. This means that a definite amount of one substance is formed, produces or reacts with a definite amount of any other. We call this: stoichiometrically equivalent molar ratios.
Step 1: The balanced equation for the reaction is: 2H2 + O2 ----> 2H2O Step 2: The molecular weight of hydrogen is 2.016. The molecular weight of water is 18.02. Step 3: Calculate the number of moles of hydrogen by dividing the weight of hydrogen by its molecular weight. Since the weight of hydrogen is given to three significant figures, there will be three significant figures in our answer. 5.15g H2 x Step 4: The desired ratio, substance desired/substance given, is:
Step 5: We multiply the ratio constructed in step 4 by the number of moles of H2 calculated in step 3 to find the number of moles of water that can be formed from the given starting amount of hydrogen. 2.55 moles H2 x Step 6: We multiply the number of moles of water by the molecular weight of water to find the weight of water that can be formed. This is the theoretical yield of water from the given amount of hydrogen assuming that plenty of oxygen is available. 2.55 moles H2O x a. Chemical reactions that involve a limiting reagent.
In a chemical reaction where arbitrary amounts of reactants are mixed and allowed to react, the one that is used up first is the limiting reactant. A portion of the other reactants remains. Balanced Reaction, Defines Stoichiometric ratios Reaction limited by syrup, There is excess ice cream and cherries. 3.5 Fundamentals of Solution Stoichiometry. A typical solution consists of a smaller amount of one substance (the solute) dissolved in a larger amount of another substance (the solvent). The concentration of a solution is usually expressed as the amount of solvent dissolved in a given amount of solution. Molarity (M) expresses the concentration in units of moles of solute per liter of solution. or
What is the molarity of a solution with 58.44 grams of NaCl dissolved in exactly 2.00 L of solution? Step One: convert grams to moles. Moles of NaCl= 58.44g NaCl x Step Two: divide moles by liters to get molarity.
Phosphorus burns in air to produce phosphorus oxide in the following reaction: 4P(s) + 5O2 (g) 1. What mass of phosphorous is needed to produce 3.25 mol of 4P(s) + 5O2 (g) a. 403 g 2. If 0.489 mol of phosphorus burns, what mass of oxygen is used? a. 15.4 g
3.2, 3.8, 3.12, 3.14, 3.18, 3.33, 3.39, 3.41, 3.44, 3.47, 3.51, 3.53, 3.55, 3.61, 3.65, 3.71, 3.75, 3.91, 3.92, 3.115, 3.120, 3.1283.137.
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Calculating the amount of water that can be formed from 5.15g of hydrogen when it reacts with plenty of oxygen.
= 2.55 moles H2
= 46.0g H2O is the amount of water that can be formed with plenty of oxygen and 5.15 g Hydrogen.
= 1.00 mol NaCl
= 0.500mol/L or 0.500M or 0.500-molar
Self check questions
P4O10(s).
After reading both the text book and the web site, take the unit quiz 
Chapter 3 problem set: Pages 125-133 
Lab: Water within a Hydrate