Hardware Models: Limiting Reagents and Theoretical Yields Lab 6 Outline Reactions in Chemistry Moles Limiting Reagents Theoretical Yield Using Analytical Balances Points of Interest Next Assignment Reactions in Chemistry Reactions are complex Gases, solids and liquids all react differently What you will be learning today are the basics only Always work with balanced reactions Balanced reactions provide us with molar ratios of reagents to products Moles We cannot make direct comparisons in chemistry using concentration or mass we use moles instead. A mole is 6.022 x 1023 of anything. This concept is similar to that of a dozen. We will be using the concept of a dozen today since 6.022 x 1023 are too many items to count out. Limiting Reagent A limiting reagent is the reagent you run out of first in a reaction. The reagent that is in excess is called, excess reagent. You must determine the limiting reagent of a reaction before you can determine the theoretical yield of product. You will be limited by mass and number of items in some of your questions today to demonstrate this point. Theoretical Yield Theoretical yield is calculated to predict how much product can be produced based on the limiting reagent calculation. You will use your predicted masses (theoretical values) to do your ratio calculations today. After the theoretical yield is established, and the actual yield obtained, one can calculate percent yield. Using Analytical Balances Each balance auto-calibrates Carefully open a door and make sure the basket is fully hinged Place a blue weigh boat on the basket Close the door completely and without slamming it Tare the boat Add the hardware and close the door carefully Record the mass to the closest 0.1 mg (0.0001 g) Remove your hardware, close the door(s) carefully and push the zero button Points of Interest Collect the required pieces of hardware from their containers. Place these in a white plastic weigh boat. The hardware may contain some oil. Wear gloves if you don’t want oil on your hands. Use the plastic weigh boat to carry your hardware. It does not fit in the balance. Use a blue plastic weigh boat in the balance to weigh your hardware. Small pieces get lost easily. Please keep track of ALL your equipment. Lab 7 Reminder Read the required reading sections in your textbook and lab manual as you prepare for Lab 7. Go through the significant figure molar mass tutorial in Blackboard before attempting the prelab questions. Use the periodic table in your lab manual. Complete and submit your pre-lab questions by the deadline. Study for the quiz. Submit your Lab 6 Report at the start of next week’s lab.