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Unformatted text preview: Topics for the day • Administrative stuff • Applications of the ideal gas law • Gas density • Chemical reactions • Partial Pressure Administrative stuff ALEKS prep chemistry assessment If you haven’t touched it for a while, you’ll get hit with a periodic assessment which you’ll have to Fnish before being able to complete more topics. ALEKS is making sure you remember what you learned. It is possible for your topic % to go down. If you had 70% on the 12th class day, I will not take away your 5%, even if you have < 70% on Monday. Quest Homework # 3 is now available. It’s due in one week at 10 am. I’ve decided to switch to weekly shorter Quest homeworks so you just get in the habit of always having Quest and ALEKS to do. Where were we? When we have stoichiometric quantities of reactants, and provided the reaction goes to completion, there will be no reactants left over. In all other situations, one reactant will be the limiting reagent for a reaction, and the amount of product made will be the amount predicted by the quantity of the limiting reagent. If the reaction goes to completion, the theoretical yield of products can be expected. The actual yield is often less than the theoretical yield. The ideal gas law can be applied to both static and perturbed systems. In addition to the gas variables of pressure, volume, temperature, and number of moles, conversions may need to be made between number of moles, and density, molecular weight, and mass. 1 2 3 Calculation Strategies for Ideal Gas Law problems Dynamic or comparison problem Which variables change? Which variables stay constant? Convert all units for consistency, remembering T must be in K. Write the initial ideal gas law with all constants on one side. Write the final ideal gas law with all constants on one side. Equate the two. Rearrange so the unknown is one side. Solve, making sure units cancel. Static problem Which variables do we know? Which variables are unknown? Convert all units for consistency, remembering T must be in K. Do you need to include stoichiometry? Rearrange the ideal gas law with the unknown on one side. Solve, making sure units cancel. Do you need to use an equation to relate n to m, M, MW, density? A sample of porous rock was brought back from another planet. Trapped in the rock was a gas. Analysis showed that only carbon and oxygen atoms were present, and that there was only one compound present. A volume of 3.70 mL of the gas was collected under STP conditions. The mass of the sample was 0.00726 g. What was the gas?...
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- Spring '09