1.3 Chemical calculations

Question 1

This may be our downfall, for such a teacher we were given it’s basically gon be solo yolo, but what is the purpose for teachers?

Answer 1

You raise a good point!

Question 2

Formula for relative atomic mass?

75% Cl-35 and 25% Cl-37

Answer 2

% x atomic number / 100
also add em at the top

(75x3)+(25x37)/100
= 35.5

Question 3

In mass spectrum:
What m/z?
What relative abundance?

Answer 3

1. Atomic number for some reason in my eyes
2. Relative atomic mass imo

Question 4

For mass spectra graph, how u gain mass for the 2 isotopes

Answer 4

Formula for mass of 2 isotopes:

(relative abundance x m/z)/ra1 + ra2

May seem a lil hard to remember but gl bro B)

Question 5

How to gain empirical formula?

48.38% carbon, 8.12% hydrogen, rest is O2 (43.50%)

% = their mass

Answer 5

mass/mr = a number
then divide that number with it (the smallest number u’ve gained)
double it if the number is not whole

48.38/12 = 4.03 divided by 2.72
8.12/1.01 = 8.02 divided by 2.72
43.5/16 = 2.72 divided by 2.72

2.72 is the smallest number

C = 1.5 x 2 = 3
H = 3 x 2 = 6
O = 1 x 2 = 2

C3H6O2

Question 6

How to gain molecular formula?

CH has molar mass of 78.1g/mol

Answer 6

mr molecular formula/mr empirical formula

CH = 12 + 1.01 = 13.01

78.1/13.01 = 6.00 = 6

C6H6

Question 7

Formula for moles?

Answer 7

Mass/molar mass = n

Question 8

How to gain mass of one molecule?

H2

Answer 8

Mr x number of atoms
then divide it by avogadro’s constant (6.02x10^23)

1.01 x 2 = 2.02 mr
2.02/6.02x10^23 = 3.36x10^-24

Question 9

How to gain number of molecules in a compound?

1.058 mole of H2O

Answer 9

n x avogadro’s constant

1.058 x (6.02x10^23) = 6.37x10^23

Question 10

How to gain moles from molar volume + volume?

120cm^3 of hydrogen at RTP (24.5 molar volume)

Answer 10

Volume (v) = number of moles (n) x molar volume (Vm)

0.12/24.5 = 0.0049 or 4.89 x 10^-3

Question 11

What is the ideal gas equation?

and what’s the 3 points to note?

Answer 11

pV = nRT

1. Temp must be kelvin (O degrees = 273K)
2. Pressure must be in pascals (1atm = 101325 Pa)
3. Volume must be m^3 (convert cm by dividing by 10^6)

Question 12

Define each symbol from ‘pV = nRT’

Answer 12

P = pressure (Pa)
V = volume (m^3)
n = number of moles (mols)
R = molar gas constant (8.31Jmol^-1 K-1)
T = temperature (K)

Question 13

What’s the simplified gas equation?

Answer 13

P1V1/T1 = P2V2/T2

Question 14

What equation if number of moles and volume remain constant?

(simplified gas equation)

Answer 14

P1/T1 = P2/T2

Question 15

What equation if number of moles and temperature remain constant?

(simplified gas equation)

Answer 15

P1V1 = P2V2

Question 16

What equation if number of moles and pressure remain constant?

(simplified gas equation)

Answer 16

V1/T1 = V2/T2

Question 17

Ig use the booklet tmrw but u rlly and probably should revise this anyway still so u can know the formulas at least

Answer 17

Yup