1. Stoichiometric Relationships

Question 1

What is kinetic energy?

Answer 1

Energy related to motion of an object

Question 2

Solid, liquid, gas: Arrangement

Answer 2

Solid: Closely packed
Liquid: Also close together but less then solid
Gas: Most spread out, far apart

Question 3

Solid, liquid, gas: Intermolecular forces

Answer 3

Solid: Strongest forces
Liquid: Weaker forces
Gas: Negligible forces

Question 4

Solid, liquid, gas: Motion

Answer 4

Solid: Vibrate at fixed positions
Liquid: Slide past each other
Gases: Move randomly

Question 5

Solid, liquid, gas: Shape

Answer 5

Solid: Fixed shape
Liquid: No fixed shape, takes shape of container
Gas: No fixed shape

Question 6

Solid, liquid, gas: Volume

Answer 6

Solid: Fixed volume
Liquid: Fixed volume
Gas: No fixed volume

Question 7

What are all the changes of state?

Answer 7

• Solid to liquid: Melting
• Liquid to gas: Evaporation
• Gas to liquid: Condensation
• Liquid to solid: Freezing
• Solid to gas: Sublimation

Question 8

What is opposite of sublimation?

Answer 8

Deposition (gas to solid)

Question 9

Why does change of state occur?

Answer 9

An increase in temperature = increase in average kinetic energy of molecules which allows them to overcome intermolecular forces and hence build or break bonds

Question 10

Examples of sublimation

Answer 10

Iodine, CO2, NHCl, Mothballs, Dry ice

Question 11

Difference between evaporation and boiling

Answer 11

• Evaporation takes place at surface and below boiling point, happens at range of temperatures
• Boiling has a specific temperature and occurs throughout the liquid

Question 12

What does flat part on heating or cooling curve show and why?

Answer 12

It shows the melting or boiling points because when there is a change of state, the temperature remains constant

Question 13

Density

Answer 13

Mass per unit volume (D= m/v)

Question 14

Unit for density

Answer 14

g/cm^3 or kg/m^3

Question 15

Element

Answer 15

Something that is made of the same kind of atom

Question 16

Compound

Answer 16

Chemically combined substance of 2 or more different elements

Question 17

Are H2 and O2 compounds?

Answer 17

No. They are molecules

Question 18

Differences between elements and compounds

Answer 18

• Elements are made of one type of atom
• Elements cannot be further broken down while compounds can be chemically
• Elements are represented by a symbol instead of formulae
• Element’s properties are determined by valence electrons while compound’s properties differ from their constituent elements
• 118 known elements while compounds have endless possibilities

Question 19

Mixture

Answer 19

2 or more substances that are not chemically combined

Question 20

Difference between mixtures and compounds

Answer 20

• Compounds are chemically combined while mixtures are physically
• Compounds are in fixed ratio
• Compounds are pure
• Compounds have a formulae
• Properties of compounds differ but mixtures retain properties of their elements/substances

Question 21

Difference between homogenous and heterogenous mixture

Answer 21

• Homogenous have uniform dispersion
• Homogenous have fixed ratio/composition
• Heterogenous are immiscible while homogenous do not physically separate on standing

Question 22

Examples of homo and heterogenous mixtures

Answer 22

Homogenous: Air, honey
Heterogenous: Sand + water, oil + water

Question 23

Are solutions homo or heterogenous?

Answer 23

Homogenous

Question 24

Solute

Answer 24

Substance that is DISSOLVED

Question 25

Solvent

Answer 25

Substance that DISSOLVES

Question 26

Concentration

Answer 26

Amount of solute dissolved per unit volume of solution

Question 27

Unit of concentration

Answer 27

g/dm^3 or mol/dm^3

Question 28

Relative atomic mass

Answer 28

Weighted average mass of an atom compared to 1/12 mass of an atom of Carbon-12

Question 29

Unit of molar mass

Answer 29

g/mol

Question 30

Avogadro's constant

Answer 30

6.02 x 10^23

Question 31

What is molar mass?

Answer 31

Mass of one mole of a substance

Question 32

How do you calculate number of moles?

Answer 32

Total mass/ Molar mass

Question 33

Calculating mass of one molecule

Answer 33

Molar mass/ Avogadro constant

Question 34

How do you find empirical formula?

Answer 34

Divide percentage by mass of element present in a mole. Find simplest whole number ratio

Question 35

What is percentage composition?

Answer 35

Mass of element in a compound/ Molar mass of compound

Question 36

How to find molecular formulae?

Answer 36

Divide mass by molar mass of empirical formula and multiply that into the empirical compound

Question 37

What are limiting and excess reagents?

Answer 37

Limiting: Limit amount of product made in a chemical reaction Excess: Reactant that remains at the end of the reaction

Question 38

How do you find excess reagent?

Answer 38

Convert elements from mass in grams to amount in mole. Divide each amount by coefficient in balanced equation. The higher value is the one in excess

Question 39

What is theoretical yield?

Answer 39

Maximum amount of product that can be produced assuming all reactant has reacted

Question 40

How do you calculate percentage yield?

Answer 40

(Actual/Theoretical yield) *100

Question 41

What is Avogadro's law?

Answer 41

States that equal volume of gas at same temp. and pressure contain equal number of particles

Question 42

What is kinetic molecular theory of gases? 5 postulates.

Answer 42

- Particles are in constant, random straight line motion - Negligible forces of attraction between particles - Collisions between particles or with surface are elastic (no energy lost) - Distance between particles > size of particles so negligible volumes - Kinetic energy is proportional to temperature

Question 43

What is molar volume?

Answer 43

Volume occupied by 1 mole of gas at STP. It is 22.7 dm^3

Question 44

Boyle's Law

Answer 44

PV=k or pressure is indirectly proportional to volume

Question 45

How do you convert Kelvin to Celsius?

Answer 45

K is Celsius + 273

Question 46

Charles' Law

Answer 46

Volume is proportional to temperature

Question 47

What is the general gas equation?

Answer 47

P1V1/T1= P2V2/T2. Units can be any as long as they are the same

Question 48

Ideal gas equation

Answer 48

``` PV= nRT where: P= Pa V= m^3 n= mol R= 8.31 J/Kmol T= K ```

Question 49

What are the conditions of a real gas?

Answer 49

Occurs at high pressure and low temp.

Question 50

Why is there greatest deviation from ideal gas in a real gas?

Answer 50

Because at low temp, they move slower and at high pressure, they are more narrowly spaced

Question 51

Why are gases like helium more ideal than real?

Answer 51

They have low molar mass and weakest intermolecular forces

Question 52

Why do NH3 and CO2 deviate greatly?

Answer 52

NH3 has strong H bonds while CO2 has very strong forces

Question 53

Under what conditions do gases behave more like an ideal gas?

Answer 53

At high temperature and lower pressure. They exhibit the 5 postulates of kinetic theory

Question 54

How do you calculate concentration?

Answer 54

Concentration= Amount of solute (mol)/volume of solution (dm^3) OR n= CV

Question 55

How do you calculate concentration for very dilute solutions?

Answer 55

It's C= n/V * 10^6. Calculated in ppm (parts per million). Note: 1ppm means 1dm^3 solution has 1 mg of solute

Question 56

What are standard solutions?

Answer 56

Solutions with precisely known concentrations - High purity - High molar mass - Low reactivity

Question 57

How would you calculate back titrations for finding CaCO3 in eggshells through HCl?

Answer 57

1. Excess HCl is reacted with aq. NaOH 2. Subtract acid reacted with NaOH from total acid reacted with egg shell to find mole of acid that reacted 3. Calculate mass of CaCO3 by moles 4. Divide mass of CaCO3 by total mass of eggshell 5. Find percentage