Chemistry exam revision Chapter 4

Question 1

What is the formula for the relative atomic mass?

Answer 1

Ar = sum of (mass x abundance) divided total abundance) x 100

Question 2

What is Mr?

Answer 2

Add up relative atomic masses of all atoms in the formula.

Question 3

What is the formula for moles?

Answer 3

moles = mass(g) divided by Mr

Question 4

What is Avagadros constant?

Answer 4

6.02 x 10 to the power of 23

Question 5

What is the limiting reagent?

Answer 5

The reactant that gets used up first in a reaction and determines amount of product?

Question 6

What is the formula for percentage yield?

Answer 6

Actual mass divided by theoretical mass x 100

Question 7

Why do we always don’t get 100% of product?

Answer 7

1. Product left behind in the apparatus
2. Reversable reactions
3. Side reactions.

Question 8

Why do we maximize atom economy?

Answer 8

1. Conserve earth rescources
2. Minimise pollution

Question 9

What is the formula for atom economy?

Answer 9

Mr of desired product divided by sum of Mr’s reactants x 100

Question 10

What is the formula for concentration?

Answer 10

concentration = moles divided by vol (dm3)

Question 11

How do we convert cm3 to dm3?

Answer 11

Divided by 1000

Question 12

How do we convert mol/dm3 to g/dm3?

Answer 12

Moles/dm3 to g/dm3 is x Mr and g/dm3 to moles/dm3 is divided by Mr

Question 13

What is the difference between a Pipette and a burrete?

Answer 13

1. Pipette - measures specific values
2. Burrete - variable volumes

Question 14

What is the end point?

Answer 14

1. “Change in color”
2. The point at which the acid has reacted completely with the alkali.

Question 15

What is the formula for volume calculations?

Answer 15

1. Vol(cm3) = moles x 24000
2. Vol(dm3) = moles x 24