Chemistry Topic 3

Question 1

What is a mole calculation

Answer 1

6.02 x 10 to the power of 23

Question 2

One mole of atoms of any substance will have a mass in grams equal to the

Answer 2

Relative formula mass

Question 3

Carbon has a relative mass of 12 so one mole of carbon weighs

Answer 3

12g

Question 4

Number of moles =

Answer 4

Mass in g/ relative mass

Question 5

Concentration 1=

Concentration2=

Answer 5

Concentration1= mass/volume 
Concentration2= number of moles/ volume

Question 6

How is mas changed-gas

Answer 6

If the gas decreases, the vessel isn’t enclosed so the gas can escape .

Question 7

Mg has a mass of 48g how many moles are there

Mr of mg= 24

Answer 7

48/24= 2mol

Question 8

Calculate the mass of four moles of NaCl.
Na= 23
Cl= 35.5

Answer 8

4 x (35.5+23)

Question 9

2g of hydrogen reacts with 71g of chlorine to make 73g of hydrogen chloride
H=1
Cl=35.5
H2+cl2-HCl

Answer 9

2g/2=1mol
71g/35.5=2mol
73g/(1+35.5) = 2mol
1h+2cl-2hcl
Divide by lowest number (1)
1/1=1
2/1=2
2/1=2
1h+ 2cl+2hcl

Question 10

1mol=

Answer 10

6.02x10-23

Question 11

Calculate the number of moles of atoms in one mole of water (h2o)

Answer 11

H2. O

^2atom. ^ 1atom = 3 atoms

Question 12

Calculate number of atoms in one mole of sodium oxide

Na2o

Answer 12

Na2. O
^2atoms ^1atoms= 3atoms
3x6.02x10-23
1.806 X 10-24

Question 13

Calculate the number of atoms in 28g of lithium

Li= 7

Answer 13

Moles= 28/7= 4
4 X 6.02 X 10-23
2.408 X 10-24

Question 14

Calculate the number of atoms in 54g of water
H=1
O=16

Answer 14

(1 X 2 ) + 16= 18
54g/ 18= 3 mol
3 X 6.02 x10-23= 1.806 X 10-24
H2.   O
^2atom ^ 1 atom= 3 atom
3 X 1.806 X 10-24 = 5.418 X 10-24

Question 15

During a chemical reaction

Answer 15

No atoms are gained or lost

Question 16

There are the same number of ______ on each side of a reaction

Answer 16

Atoms

Question 17

If the mass increases during a reaction it’s because

Answer 17

One of the reactants is a gas which is found in the air and it reacts to form part of the product

Question 18

Is the mass decreases during a raeaction it’s because

Answer 18

One of the products is gas and gas can escape

Question 19

The reaction that’s used up is called e

Answer 19

Limiting reactant

Question 20

Reactions stop when

Answer 20

All of one reactant is used up

Question 21

The amount of product formed is ___________ to the amount of limiting reactant

Answer 21

Directly proportional

Question 22

Concentration is a measure

Answer 22

Of how crowded things are

Question 23

The amount of substance in a given volume is

Answer 23

Concentration

Question 24

Solute is

Answer 24

Substance that’s dissolved

Question 25

Volume unit

Answer 25

Dm3

Question 26

The atom enconommy tells us

Answer 26

How much of the mass of the reactants is wasted when manufacturing a chemical and how much ends up useful

Question 27

Atom enconomy=

Answer 27

Mr of desired product/

mr of all reactants X 100

Question 28

Night atom enconomy is better for

Answer 28

Profits and the environment

Question 29

Percentage yield compares

Answer 29

Actual and theoretical yield

Question 30

Percentage yield=

Answer 30

Mass of product acc made/

Macimiumum theoretical mass of product X100

Question 31

Percentage yield and atom enconomy is always between

Answer 31

0% and 100%

Question 32

Why yields are always less than 100%

Answer 32

Not all reactants react to make product
There might be side reactions
You lose some product when you separate it from reaction mixtures