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 complexGases, solids and liquids all react

differentlyWhat you will be learning today are the

basics onlyAlways work with balanced reactionsBalanced 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 pre-lab 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.