Hardware Models: Limiting Reagents and Theoretical Yields Lab 6

Outline Reactions in Chemistry Reactions in Chemistry Moles Moles Limiting Reagents Limiting Reagents Theoretical Yield Theoretical Yield Using Analytical Balances Using Analytical Balances Points of Interest Points of Interest Next Assignment Next Assignment

Reactions in Chemistry Reactions are complex Reactions are complex Gases, solids and liquids all react differently Gases, solids and liquids all react differently What you will be learning today are the basics only What you will be learning today are the basics only Always work with balanced reactions Always work with balanced reactions Balanced reactions provide us with molar ratios of reagents to products 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. We cannot make direct comparisons in chemistry using concentration or mass - we use moles instead. A mole is x of anything. A mole is x of anything. This concept is similar to that of a dozen. This concept is similar to that of a dozen. We will be using the concept of a dozen today since x are too many items to count out. We will be using the concept of a dozen today since x are too many items to count out.

Limiting Reagent A limiting reagent is the reagent you run out of first in a reaction. A limiting reagent is the reagent you run out of first in a reaction. The reagent that is in excess is called, excess reagent. 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 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. 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. 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. 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. After the theoretical yield is established, and the actual yield obtained, one can calculate percent yield.

Using Analytical Balances Each balance auto-calibrates Each balance auto-calibrates Carefully open a door and make sure the basket is fully hinged Carefully open a door and make sure the basket is fully hinged Place a blue weigh boat on the basket Place a blue weigh boat on the basket Close the door completely and without slamming it Close the door completely and without slamming it Tare the boat Tare the boat Add the hardware and close the door carefully Add the hardware and close the door carefully Record the mass to the closest 0.1 mg ( g) Record the mass to the closest 0.1 mg ( g) Remove your hardware, close the door(s) carefully and push the zero button 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. Collect the required pieces of hardware from their containers. Place these in a white plastic weigh boat. 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. 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 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. 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. 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. 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 pre- lab questions. Go through the significant figure molar mass tutorial in Blackboard before attempting the pre- lab questions. Use the periodic table in your lab manual. Use the periodic table in your lab manual. Complete and submit your pre-lab questions by the deadline. Complete and submit your pre-lab questions by the deadline. Study for the quiz. Study for the quiz. Submit your Lab 6 Report at the start of next week’s lab. Submit your Lab 6 Report at the start of next week’s lab.