Quantitative Chemistry: Moles and more

Question 1

What are the equations for Average atomic mass and Mr

Answer 1

Ar=(Isotope mass x abundance) + (Isotope mass x abundance)/100
Mr=atomic mass+ atomic mass like Co2 is (16x2)+12

Question 2

How do you calculate percentage mass of Aluminium in Al203

Answer 2

1.Calculate Mr 2x27=54
2.Then the total Mr is 16 x 3= 48 leading to 48+54=102
3. 54/102x100=52.9%

Question 3

WHat is the mol equation

Answer 3

Mol=Mass/mr

Question 4

Calculate the number of moles in 50g of Calcium

Answer 4

50g/40mr=1.25mol

Question 5

What is avogadros constant

Answer 5

6.02x10^23 atoms ions or molecules

Question 6

How do you use Avagadros constant to find the mass of a single ion/atom/molecule

Answer 6

Mr/6.02x10^23
example Na mr is 23 so
23/6.02x10^23

Question 7

Conservation of Mass

1600 tonnes of iron oxide reacts with an unknwn mass of carbon to produce 660 tonnes of carbon dioxide and 1120 tonnes of iron.

Answer 7

660+1120=1780
1780-1600=180
Carbon=180 tonnes

Question 8

Why would the reaction between magnesium and oxygen see an increase in mass in the products

Answer 8

Due to oxygen being a gas at room temperature it cannot be measured the gas will bond with the magnesium cauisng it to gain mass.

Question 9

In a reaction iron oxide reacts with carbon to produce carbon dioxide and iron.

Answer 9

2Fe2O3+3C->3CO2+4Fe
M 500/ ** 350g**
Mr 160 56x
Mol 3.25
(3.25/2)x4 to get ratio=6.25

Question 10

How to balance equations using moles

Answer 10

1 Write Mass Mr Mol and columns
2 Calculate mr and mols using equations
3Divide each mol value by the smallest value. If it becomes a decimal find a common multiple
4Then the number found put on the thing to balance it

Question 11

What is the limiting reagent and excess

Answer 11

This is the substance in the reaction that reacts fully with everything and has the same amount of moles as the product. Excess does not react fully leaving moles behind

Question 12

What is the concentration of solutions eqaution and units

Answer 12

Concentration g/dm^3=Mass g/Volume dm^3

Question 13

How to get to decimetres cubed

Answer 13

divide subject in cm by 1000
so 70/1000=0.07

Question 14

Concentration of moles equation and units

Answer 14

Concentration mol/dm^3=Moles of solute mol/volume of solution dm^3

Question 15

Atom economy equation

Answer 15

Rfm of desired product/Rfm of all reactants x 100

Question 16

Percentage Yield equation and volume of gas

Answer 16

Actual/Theoretical x 100
Volume of gas=Mol number x gas volume(24 dm^3)