Amount of Substance

Question 1

What is the symbol for amount of substance?

Answer 1

n

Question 2

What is the unit used to measure amount of substance?

Answer 2

Mole

Question 3

What does the Avagadro constant represent?

Answer 3

The number of atoms per mole of the carbon-12 isotope.

Question 4

How to calculate the mass of 1 mole of the element?

Answer 4

Mass of 1 mole = relative atomic mass in grams

Question 5

How to calculate moles when mass and molar mass are given?

Answer 5

Moles = mass/ RFM

Question 6

State Avagadro Law

Answer 6

Under the same temperature and pressure, one mole of any gas would occupy the same volume.

Question 7

How much volume does a gas occupy at room temp and pressure?

Answer 7

24 dm^3

Question 8

Define molar gas volume

Answer 8

The volume per mole of gas molecules

Question 9

Why do different gas particles occupy the same volume?

Answer 9

The gas particles are very spread out, hence individual differences has no effect

Question 10

How to calculate moles when gas volume is given?

Answer 10

Moles= volume (dm3) / 24

Question 11

What are the ideal ways in which gases behave?

Answer 11

They are in continuous motion.
No intermolecular forces are experienced
Exert pressure when they collide with each other or container.
No kinetic energy is lost in the collisions
When temperature increases, kinetic energy of gases also increase

Question 12

The ideal gas equation

Answer 12

pV=nRT 
Pressure in Pa
Volume in m^3
N is number of moles
Gas constant on 8.314. 
Temperature in K

Question 13

1 atm is equal to how many pascals?

Answer 13

1 atm= 101325 Pa

Question 14

0 Celsius is equal to how many kelvin

Answer 14

273

Question 15

What does concentration of a solution mean?

Answer 15

It is the amount of solute dissolved in a dm3 of solvent.

Question 16

How do you calculate moles when concentration and volume are given?

Answer 16

Moles= concentration x Volume

Question 17

What is a standard solution?

Answer 17

A solution of known concentration

Question 18

Write down the steps to prepare a standard solution

Answer 18

1. Weigh the solute using the weigh by difference method
2. In a beaker dissolve the solute using the solvent.
3. Pour the solution into a volumetric flask.
4. Rinse the beaker using the solution and add it to the flask.
5. Add solvent to the flask carefully until it reaches the graduation line.
6. Mix the solution throughly to ensure complete mixing.

Question 19

What do the terms concentrated and dilute mean?

Answer 19

Concentrated- large amount of solute per dm^3
Of solvent.
Dilute- small amount of solute per dm^3 of solvent.

Question 20

What is a species in a chemical reaction?

Answer 20

Any particle that takes part in a reaction

Question 21

What are the four common state symbols?

Answer 21

1. Solid
2. Liquid
3. Gaseous
4. Aqueous

Question 22

What does percentage yield mean?

Answer 22

The efficiency of which reactants are converted into products.

Question 23

What are the reasons for not obtaining 100% yield?

Answer 23

Reaction may be at equilibrium.
The reactants may be impure
Side reactions can be happening
Reactants and products may be left behind while transferring.
Loss of products during separation and purification.

Question 24

How is percentage yield calculated?

Answer 24

Actual mol/ theoretical mol x100

Question 25

What does atom economy tell us about

Answer 25

The proportion of desired products compared with all the products formed in the reaction

Question 26

How is atom economy calculated ?

Answer 26

Molecular mass of desired product/ sum of the molecular masses of all products x 100

Question 27

Does 100% yield mean 100% atom economy?

Answer 27

No, even if all the reactants are converted into products, not all products of the reaction will be the required products,

Question 28

Which type of reaction has a 100% atom economy?

Answer 28

Addition reactions- where 2 or more reactants are combined to form A product