2.1.3 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 Avogadro 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 do you calculate moles when mass and molar mass are given?

Answer 5

Moles (mol) = mass (g) / molar mass (g/mol)

Question 6

State Avagadro’s 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 temperature and pressure?

Answer 7

24 dm³

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 volume is given?

Answer 10

Moles (mol) = volume (dm³)/24

Question 11

What are the ideals ways in which gases behave

Answer 11

• They are in continuos motion
• No intermolecular forces experienced
• Exert pressure when they collide with each other or container
• No kinetic energy is lost in collisions
• When temperature increases, kinetic energy of gasses also increases

Question 12

Write down the ideal gas equation

Answer 12

pV=nRT

Pressure (Pa) x volume (m³) = Moles (mol). x gas constant (8.314 J/mol) x temperature (K)

Question 13

1 atmospheric pressure is equal to how many pascals?

Answer 13

1 atm = 101325 Pa

Question 14

0°C is equal to how many kelvin?

Answer 14

273K

Question 15

What does concentration of a solution mean?

Answer 15

It is the amount of solute dissolved in 1 dm³ of solvent

Question 16

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

Answer 16

Moles (mol) = concentration (mol/dm³) x volume (dm³)

Question 17

What is a standard solution?

Answer 17

A solution of known concentration

Question 18

What does the terms concentrated and dilute mean?

Answer 18

Concentrated - large amount of solute per dm³ of solvent

Dilute - small of solute per dm³ of solvent

Question 19

What is a species in a chemical reaction?

Answer 19

Any particle that takes part in a reaction

Question 20

What are the four common state symbols?

Answer 20

1. Solid (s)
2. Liquid (l)
3. Gaseous (g)
4. Aqueous. (aq)

Question 21

What does percentage yield mean?

Answer 21

The efficiency of which reactants are converted into products

Question 22

What are the reasons for not obtaining 100% yield?

Answer 22

• Reactions may not be at equilibrium
• The reactants may be impure
• Side reactions may happen
• Reactants or products may be left behind while transferring
• Loss of products during separation and purification

Question 23

How is percentage yield calculated?

Answer 23

Percentage yield = (actual amount of product (mol) / theorectical amount of product (mol)) x 100

Question 24

What does atom. economy tell us about?

Answer 24

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

Question 25

How is atom economy calculated?

Answer 25

Atom economy = (molecular mass. of desired product / sum of the molecular masses of all products) x 100

Question 26

Does 100% yield mean 100% atom economy?

Answer 26

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

Question 27

Which type of reaction has 100% atom economy?

Answer 27

Addition reactions (two or more reactants are combined to form a product)