Relative atomic and molecular masses, the mole and the Avogadro constant

Question 1

Concentration (the amount of solute in moles dissolved per 1dm3 of solution) =

Answer 1

Moles/Volume

Question 2

Number of Moles Calc =

Answer 2

mass/Mr

Question 3

1 Moles. concentration (mol/dm1)

Answer 3

moles (mol) / volume (dm3)

Question 4

1. cm3 - dm3

Answer 4

/1000

Question 5

1. moles (mol)=

Answer 5

Mass (g) / Mr (Ar)

Question 6

1. 1 mole of an atom =

Answer 6

Ar in g

Question 7

1. 1 mol of a molecule =

Answer 7

Mr in grams

Question 8

1. it takes 32.10cm3 of HCl, concentration of 0.0150 mol dm-3, to complete react with 25.00cm3 of sodium hydroxide solution. Calc the conc of NaOH solution.

HCl +NaOH

Answer 8

c = mol/vol.

moles HCl = 0.150 x (32.10/1000) = 4.815 x 10-3
therefore moles of NaOH = 0.004815
Conc of NaOH = 0.004815 / (25/1000) = 0.193 moldm-3

Question 9

1. (NH4)2SO4 + 2NaOH
   3.14g of ammonium sulphate reacted completely with 39.30cm3 of NaOH

a. Moles in (NH4)2SO4 in 3.14g

Answer 9

3.14/Mr (132.1) = 0.0237698 = 0.0238

Question 10

1. (NH4)2SO4 + 2NaOH
   3.14g of ammonium sulphate reacted completely with 39.30cm3 of NaOH

b. Moles in NaOH

Answer 10

ratio= 1:2
moles 0.0238x2= 0.0476

Question 11

1. (NH4)2SO4 + 2NaOH
   3.14g of ammonium sulphate reacted completely with 39.30cm3 of NaOH

c. Conc of NaOH used

Answer 11

conc= moles/vol = 0.0476/(39.3/1000) = 1.21 mol dm-3

Question 12

1.Zn0+2HCl
0.0830 of ZnO added to 100cm3 of 1.20 mol dm-3 HCl. Calc maximum mass of ZnCl

Answer 12

mols HCl = conc x vol = 1.20 x 100/1000 = 0.12 therefore moles of ZnCl2 = 0.06
mass ZnCl2 = moles x Mr = 0.06 x (65.4+(35.5x2))
=8.184=8.18g

Question 13

2 Ideal Gas.

Answer 13

One Mole of Any Gas = 24dm3 (100KPa, 298K)

Question 14

2. Formula

Answer 14

p(pressure Pa) V (Volume m3)=n (no.mols)R(Gas constant)T(K)

Question 15

2. How do you convert Celsius to Kelvin formula?

Answer 15

Celsius to Kelvin: Kelvin = Celsius + 273

Question 16

2. 4NH3+502 - 4NO + 6H2O
   total volume of 4.31m3 at 25C and 100kPa
   Calc Moles of NO produced
   (R= 8.31J K-1mol-1)

Answer 16

Pv=nRT therefore n = Pv/rt = 100000(100KPa x1000)x4.31/8.31x(25+273) = 174
Moles = 174 = total gasses
Moles of NO= (174/10(4+6)) X 4 = 69.6 Of NO

Question 17

2. B203 + 3C + 3Cl2 - 2BCl3 + 3CO
   Boron oxid reacted completely with C and Cl. Two Gases total volume of 5000cm3 at pressure of 100kPa and Temp of 298K. Calc Mass. (R=8.31J)

Answer 17

cm3 - dm3 = divide by 1000
pV=nRT therefore pv/RT= 100000(x1000 to Pa)x(5000/1000000) / 8.13 x 298 = 0.2019
Moles of B2O3 = 0.2019/5 = 0.0403815
Moles=Mass/Mr - Mass of B2O3: moles x Mr = 0.040 x ((10.8x2)+(16x3)) = 2.81g

Question 18

2. MgNO3 secomposed to produce 0.402mol of gas. Calc volume thats would occupy at 333K and 1.00x105Pa. (R=8.31J)

Answer 18

Pv=nRT therefore v = nRT/P = 0.402 x 8.31 x 333 / 1x10^5 = 0.0111242 m3 x 1000 = 11.1dm3

Question 19

2. cm3 - dm3 - m3 =

Answer 19

divide by 1000

Question 20

3. Theoretical And percentage yield

Answer 20

Percentage yield - what we actually get
Theoretical - Max we could get if the experiment was 100% perfect

Question 21

30g of C3H8 burns in the air to produce 70g OF CO2. calc theoretical and % of CO2.

Answer 21

1C3H8 (limiting)+ 3O2 (excess) - 4H20 + 3C02
1. Identify Limiting and Excess
C3H8 - 3C + 8H
= 3(12)+8(1) = 44.094g/mol
30g C3H8/1 x 1mol C3H8/44.094gC3H8 x 3moCO2/1molC3H8

Question 22

Percentage yield =

Answer 22

Actual / theoretical x 100%

find no of moles
then divide them both
x 100

Question 23

Moles in Masses =

Answer 23

use Moles = n/Mr and Vol (dm3) = n x 24 dm3 (“Molecular Gas Volume”)

Question 24

triangles

Answer 24

mass = mol x Mr
Volume = mol x 24 dm3
conc = n/v

Question 25

Empirical and molecular

Answer 25

mass:
divide by Mr = moles
divide by smallest no.

Question 26

1 mole

Answer 26

contains 6.02 x 10^23

Question 27

Calculate the mass of sodium hydroxide, NaOH, required to prepare 250 cm3 of a 0.200 mol dm-3 solution

Answer 27

Step 1: Find the number of moles of NaOH needed from the concentration and volume:

number of moles = concentration (mol dm-3) x volume (dm3)
n = 0.200 mol dm-3 x 0.250 dm3
n = 0.0500 mol
Step 2: Find the molar mass of NaOH

M = 22.99 + 16.00 + 1.01 = 40.00 g mol-1
Step 3: Calculate the mass required

mass = moles x molar mass
mass = 0.0500 mol x 40.00 g mol-1 = 2.00 g

Question 28

volumetric solutions

Answer 28

1- Weigh out a precise amount of the solid
2- Add to a small volume of water & pre - dissolve the solid (glass rode)
3-

Question 29

How to make a standard solution

Question 30

Concentration is usually expressed in one of three ways:

Answer 30

moles per unit volume
mass per unit volume
parts per million

Question 31

The concentration of a solution is the amount of solute dissolved in a solvent to make 1 dm3 of solution
The solute is the substance that dissolves in a solvent to form a solution
The solvent is often water
A concentrated solution is a solution that has a high concentration of solute

Question 32

A dilute solution is ?

Answer 32

a solution with a low concentration of solute

Question 33

A concentrated solution?

Answer 33

is a solution that has a high concentration of solute

Question 34

The concentration of a solution is?
The solvent is often water

Answer 34

the amount of solute dissolved in a solvent to make 1 dm3 of solution
The solute is the substance that dissolves in a solvent to form a solution