Topic 1: Stoichiometry

Question 1

What is a homogenous mixture

Answer 1

All substances in mixture in the same phase (NOT STATE) essentially everything is mixed so well you can’t see the difference between them - no visible boundary separating it into parts.

Question 2

What is a heterogenous mixture

Answer 2

Substances all in different phases

Question 3

Mixtures and their individual properties

Answer 3

They retain their individual properties/they are not chemically bonded

Question 4

Describe a solid

Answer 4

Fixed shape
Can vibrate about a fixed point
Heat can cause enough vibration to overcome attractive forces –> melts

Question 5

Describe a liquid

Answer 5

Takes shape of container, fixed volume
Has translational velocity (diffusion)
Heat and pressure of vapour can cause it to boil and evaporate

Question 6

Describe a gas

Answer 6

Widely spaced particles, fill container
Pressure in a container is caused by collisions with the container
IMF is negligible

Question 7

Solid to gas

Answer 7

Sublimation

Question 8

Gas to solid

Answer 8

deposition

Question 9

liquid to gas without boiling

Answer 9

vaporization

Question 10

Liquid to solid

Answer 10

freezing

Question 11

gas to liquid

Answer 11

condensation

Question 12

is vaporization endo or exo

Answer 12

endothermic because it absorbs energy to increase kinetic energy to change to a vapour

Question 13

What is avagadros constant

Answer 13

6.02 *10^23

Question 14

What is an isotope

Answer 14

Same amount of protons and electrons but different mass –> different amount of neutrons

Question 15

Symbol for relative mass

Answer 15

Mr

Question 16

Mole to atoms

Answer 16

1 mole to 6.02*10^23 atoms

Question 17

mole to mass to molar mass formula

Answer 17

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

Question 18

Empirical formula

Answer 18

The smallest whole number ratio of atoms in an element

Question 19

How to calculate empirical formula given percentage mass

Answer 19

1. assume 100 g total and change each percentage to grams
2. convert to mols by dividing by molar mass
3. find ratio between the grams and multiply accordingly

Question 20

How to calculate molecular formula from empirical formula given its molar mass

Answer 20

1. divide given molar mass by the mass of the empirical formula
2. multiply subscripts by the number found in step 1

Question 21

What is a precipitate

Answer 21

insoluble ionic solid

Question 22

Density of liquid formula

Answer 22

Mass (g)/Volume (cm^3)

Question 23

Ideal gas law and all of the units

Answer 23

PV = nRT
Pressure (1 atm - 1.013 * 10^5 Pa)
Volume (1 m^3 - 1000 litres)
Moles
R constant (8.314 J/K*mol)
Temperature (kelvin)

Question 24

What are moles represented by in an equation

Answer 24

the coefficients in front of them

Question 25

what does (aq) mean

Answer 25

in aqueous solution

Question 26

Properties of chemical reactions

Answer 26

1. new substances are formed 2. Bonds in the reactants are broken and bonds int he products are formed resulting in an energy change between the reacting system and its surroundings 3. There is a fixed relationships between the number of particles of reactants and products --> no overall change in mass

Question 27

What are net ionic equations

Answer 27

Only show species between oxidized or reduced - elimination of spectator ions 1. write molecule equation 2. write complete ionic equation showing all aqueous species broken down into their ions 3. cancel out spectator ions that appear on both sides.

Question 28

When to use ionic equations and why

Answer 28

When dealing with ionic compounds because they completely dissociate in solution

Question 29

units of concentration/formula

Answer 29

C=n/V (mols dm^-3)

Question 30

[ ] meaning

Answer 30

concentration

Question 31

At constant temperature what happens between volume and pressure

Answer 31

Volume decrease causes increase in gas concentration and pressure from collisions with container walls. Therefore greater pressure. Pressure increase is inversely proportional to decrease in volume

Question 32

when does a gas behave most like an ideal gas?

Answer 32

At high temperatures and low pressures

Question 33

At stp what volume does one mol of gas occupy

Answer 33

22.7 dm^3 or 22.7 * 10^-2 m^3

Question 34

Atom economy formula

Answer 34

atom economy = mass of desired products/mass of all products * 100

Question 35

Magnitude of atom economy meaning

Answer 35

high atom economy means that fewer natural resources are used and less waste is created

Question 36

Percentage yield formula?

Answer 36

Actual yield/theoretical yield * 100

Question 37

Percentage change formula

Answer 37

(Final - initial) / initial * 100

Question 38

percentage error calculation

Answer 38

(actual value - expected value)/expected value * 100