chemical quantities, reactions and equilibrium

Question 1

what is 1 mole

Answer 1

6.02 x 10*23 (which is avogadro’s number)

Question 2

when was avogadro’s number (1 mole) developed

Answer 2

1811

Question 3

in a calculation what do brackets suggest

Answer 3

that we have to multiply everything in the bracket by the number outside it

Question 4

what is molar mass

Answer 4

this is the mass of a compound divided by the moles (g/mol)

Question 5

how do we calculate molar mass

Answer 5

mass/ amount in moles (n)

Question 6

how do we calculate mass

Answer 6

molar mass x amount in moles

Question 7

how do we calculate moles

Answer 7

mass/ molar mass

Question 8

what is concentration

Answer 8

the amount of a substance in a defined volume

Question 9

what are the units of concentration

Answer 9

molarity (M)

Question 10

how do you calculate concentration

Answer 10

molarity (M)= moles (mol)/ volume (L)

Question 11

how do you calculates moles of a solution

Answer 11

molarity x volume

Question 12

how do you calculate the volume of a solution

Answer 12

moles/ molarity

Question 13

if you see a volume with ml as units what do you do

Answer 13

convert it into L by dividing it by 1000

Question 14

what is the calculation for dilution

Answer 14

C1 x V1 = C2 x V2

Question 15

what does C1 and V1 stand for

Answer 15

initial concentration and initial volume

Question 16

what does C2 and V2 stand for

Answer 16

final concentration and final volume

Question 17

what is the calculation for initial concentration

Answer 17

C2 x V2/ V1

Question 18

what the calculation for initial volume

Answer 18

C2 x V2/ C1

Question 19

what’s the calculation for final concentration

Answer 19

C1 X V1/ V2

Question 20

what’s the calculation for final volume

Answer 20

C1 X V1/ C2

Question 21

what are reversible reactions

Answer 21

a reaction that can go forward and back

Question 22

what is an example of a reversible reaction

Answer 22

N2 + 3H2= 2NH3
2NH3= N2 + 3H2

Question 23

what is equilibrium

Answer 23

when a forward reaction equal to the rate of the reverse reaction

Question 24

what is the equation to represent equilibrium

Answer 24

rate F = rate R
(forward) (reverse)

Question 25

describe what happens at equilibrium

Answer 25

the rate of the forward reaction is equal to the rate of the reverse reaction. the conc is changing but the reaction isn’t stopped

Question 26

describe how equilibrium works for N2 + 3H2 = 2NH3

Answer 26

at the beginning of the reaction there is a lot of N2 and 3H2 and as the reaction continues the conc of N2 and 3H2 decreases. then the conc of 2NH3 increases. Finally, after dynamic equilibrium has been reached the concentrations don’t change anymore and the forward and reverse reactions are equal

Question 27

what is the calculation for equilibrium constants

Answer 27

Kc= [D]d [E]e / [A]a [B]b
(the products are on top and reactants are on the bottom)

Question 28

what does Kc show

Answer 28

shows the ratio of products and reactants at equilibrium

Question 29

when adding molecules into the equilibrium constant equation where do you place the coefficient (number in front of molecule)

Answer 29

make it an exponent (as a power, number at the top)

Question 30

what are the units of Kc

Answer 30

moles per litre

Question 31

when was le chatelier principle developed

Answer 31

1884

Question 32

what is le chatelier’s principle

Answer 32

if stress is applied to a system in dynamic equilibrium the system will be adjusted to relieve the stress

Question 33

what happens when the pressure is increased but the volume is decreased

Answer 33

this favours the side with fewer moles so equilibrium is moved to the right

Question 34

what happens when there is increased volume but decreased pressure

Answer 34

this favours the side with the most moles so equilibrium is moved to the left

Question 35

describe what temperature does to the equilibrium constant

Answer 35

• when temperature changes so does Kc
• when the forward reaction is exothermic (releases heat = temp decreases) the reverse reaction is endothermic (takes in heat= temp increases)