mod 2

Question 1

what is stoichiometry?

Answer 1

refers to the quantities of chemicals involved in a chemical reaction and how these are calculated

Question 2

why is stoichiometry important?

Answer 2

• know how much reactant is needed in a chemical reaction
• can predict how much each product will make
• know which reactant may be in excess
• know which is the limiting reagent that is preventing more of the product(s) from being made

Question 3

what is molar mass (g)?

Answer 3

sum of Avg. atomic mass of each type of atom and how many there are in a chemical formula

Question 4

no. of moles formula?

Answer 4

mass / molar mass or n=m/MM

Question 5

what is the percentage composition of a compound?

Answer 5

% composition by mass = mass of element / mass of compound x 100

Question 6

what is the empirical formula?

Answer 6

the empirical formula is the chemical formula of a compound expressed in its simplest whole ratio of elements

Question 7

what is a molecular formula?

Answer 7

it’s a multiple of the empirical formula
multiple number = molar mass of compound / molar mass of empirical formula

Question 8

what is the molarity formula?

Answer 8

concentration (M) = moles of solute / volume of solution
c = n/v

Question 9

what is a solution?

Answer 9

a solution consists of a solute dissolved in a solvent

Question 10

what is concentration?

Answer 10

concentration refers to the amount of solute dissolved in a solution

Question 11

how can we measure concentration?

Answer 11

• % composition by mass or grams of solute per 100g of solution (%w/w)
• mass of solute per litre of solution i.e. grams per litre (g.L-1)
• moles of solute per litre of solution i.e moles per litre (mol.L-1) or molar (M)

Question 12

what are less measures of concentration?

Answer 12

• percentage by volume (%v/v)
  concentration = volume of solute in ML / volume of solution in ML x 100
• percentage mass/volume (%m/v)
  concentration = mass of solute in g / 100ML of solution x 100

Question 13

how can you use molarity?

Answer 13

• how many moles has been used in a chemical reaction with a solution
• what mass of a solute is needed to make a solution with a set concentration

Question 14

what is a standard solution?

Answer 14

a solution is any solution whose concentration is known accurately

Question 15

how can standard solutions be used?

Answer 15

• to manufacture chemicals
• to test other chemicals or materials
• to determine the concentration of other solutions by being used to react in water

Question 16

what is a primary solution?

Answer 16

is a term given to a chemical that can exist in pure form so that the number of moles can be accurately calculated from its measured mass

Question 17

how can you use molarity in dilution?

Answer 17

• no. of moles before dilution = no. of moles of sample after dilution
• concentration = moles. of solute/volume of solution
• C1V1 = C2V2

Question 18

what is titration?

Answer 18

a technique to determine the concentration of a solution (analyte) by reacting small volumes of it with a known volume of a standard solution (titrant)

Question 19

what makes a good primary solution?

Answer 19

• can be stored without deteriorating or reacting with the atmosphere
• doesn’t absorb water from the atmosphere
• high molar mass to minimise error in measurement

Question 20

how to analyse titration volume

Answer 20

1. write balanced equation for reaction in conical flask
2. calculate moles of standard solution
3. n = c x v
4. use mole ratios in the balanced equation to calculate the unknown test solution
5. calculate the concentration of the test solution - c = n/v

Question 21

particle kinetic theory

Answer 21

particles of a gas are far apart and exert no force of attraction on each other; instead they have a large amount of kinetic energy and zoom past each other

Question 22

corollary of particle kinetic theory

Answer 22

• gases occupy the full volume of their container
• gases are compressible
• gases have low density

Question 23

what is gas pressure?

Answer 23

the amount of force per unit surface area is measured when gas particles hit the floor, walls and lid of their container when they exert a force

Question 24

formula for gas pressure?

Answer 24

pressure = force/area

Question 25

1 bar = ?

Answer 25

= 100 000 Pa = 100 kpa

Question 26

1 newton of force per square metre = ?

Answer 26

= 1 pascal (Pa)

Question 27

1 atmosphere (atm) = ?

Answer 27

= 760 mmgh = 101.3 kpa

Question 28

what is Boyle’s law

Answer 28

pressure is inversely propotion to volume for a gas at constant temperature
- as the pressure decreases, the volume increases and vice versa

Question 29

boyle’s law formula?

Answer 29

P1V1 =P2V2

Question 30

what is charle’s law?

Answer 30

volume is indirectly proportional to temperature for a gas at constant pressure
- as the temperature of a gas decreases, the volume of the gas decreases
- vice versa

Question 31

charle’s law formula?

Answer 31

v1/t1 = v2/t2

Question 32

what is Gay-Lursac’s law?

Answer 32

pressure is directly proportional to temperature (in K) for a gas at constant volume
- as the temperature of a gas is decreased, the pressure of the gas decreases
- vice versa

Question 33

Gay-Lursac’s formula?

Answer 33

p1/t1 = p2/t2