chemistry equations

Question 1

R.A.M (Ar) =

Answer 1

∑(isotopic mass x % abundancy)/ 100 (no units)

Question 2

R.M.M (Mr) =

Answer 2

∑Ar of all atoms in chemical formulae (no units)

Question 3

= Mr

Answer 3

Molar mass (M)/ g mol-1

Question 4

Moles/ mol =

Answer 4

mass (g)/ M (g mol-1)

Question 5

Moles of a gas @ R.T.P/ mol =

Answer 5

volume (dm3)/ 24 (dm3 mol-1)

Question 6

Concentration/ mol dm-3 =

Answer 6

moles (mol)/ volume (dm3)

Question 7

Concentration/ g dm-3 =

Answer 7

mass (g)/ volume (dm3)

Question 8

Concentration/ g dm-3 =

Answer 8

concentration (mol dm-3) x M (g mol-1)

Question 9

Using the molar gas volume @ RTP: moles (mol)

Answer 9

= volume (dm3)/ Vm

Question 10

where RTP =

molar gas volume =

Answer 10

room temperature & pressure (20oC & 101 kPa) Vm = 24.0 dm3 mol-1

Question 11

Ideal Gas Equation:

Answer 11

pV = nRT

Question 12

where p = 
V = 
n = 
mol R =
T =

Answer 12

pressure/ kPa or Pa
volume/ dm3 or m3 moles/
molar gas constant 8.314 J mol-1 K-1
temperature/ K

Question 13

% yield =

Answer 13

actual yield (g) / theoretical yield (g) x 100

Question 14

% atom economy =

Answer 14

mass of desired product from balanced equation / total mass of reactants from balanced equation
x 100

Question 15

ΔrH =

Answer 15

∑E(bonds broken)- ∑E(bonds formed)

where ΔH = enthalpy change of reaction/ kJ mol-1 E = bond enthalpy/ kJ mol-1

Question 16

ΔrH =

Answer 16

∑(ΔfH products) - ∑(ΔfH reactants)

where ΔrH = enthalpy change of reaction/ kJ mol-1 ΔfH = enthalpy change of formation/ kJ mol-1

Question 17

ΔrH =

Answer 17

∑(ΔcH reactants) - ∑ ΔcH(products)

where ΔrH = enthalpy change of reaction/ kJ mol-1 ΔcH = enthalpy change of combustion/ kJ mol-1

Question 18

q =

where 
q =
m=
 c =
 T=

Answer 18

mcΔT

heat transferred to or from water/ J

mass of water/ g

specific heat capacity of water/ 4.18 J g-1 K-1 Δ

change in temperature in water/ K

Question 19

ΔH =

enthalpy topic

Answer 19

ΔH = q/n

Question 20

Rate of reaction =

Answer 20

gradient = change in Y /
change in X

Question 21

Equilibrium constants for the general reaction

Answer 21

: aA + bB ⇌ cC + dD

Question 22

Kc =

Answer 22

[C]c[D]d / [A]a[B]b

Question 23

General formula of an alkane =

Answer 23

CnH2n+2

Question 24

General formula of an alkene =

Answer 24

CnH2n

Question 25

General formula of an alkyl group =

Answer 25

CnH2n+1

Question 26

k =

where k = rate constant/

Answer 26

ln2/ t1/2

s-1 t1/2 = half-life/ s

Question 27

k =

where k = rate constant/ various rate

Answer 27

A e-Ea/RT , taking natural logs, ln k = -Ea/ RT + ln A

Question 28

k = 
 A =
Ea =
 R = 
T =

Answer 28

k = rate constant/ various units
 A = pre-exponential factor/ same units as k 
Ea = activation energy/ J mol-1
 R = gas constant = 8.314 J mol-1 K-1 
T = temperature/ K

Question 29

Equilibrium gas constant, Kp, for the general reaction:

Answer 29

aA + bB ⇌ cC + dD

Question 30

Kp =

Answer 30

p(C)c x p(D)d / p(A)a x p(B)b