Chapter 3 amount Of Substance And The Mole

Question 1

What is a mole

What it’s avagadros constant

Answer 1

The amount of substance that contains 6x 10 ^23 particles

2) the number of particles in one mole of carbon 12, 12g of carbon 12 contains 6x10^23

Question 2

Remember which atoms exist as molecules?

Answer 2

Honfatbricl, and P4 and S8

Question 3

Empirical formula

Answer 3

Simplest whole number ratio of atoms of each element in a compound

Question 4

What is relative molecular mass

Answer 4

Is the mass of a molecule compared with the mass of 1/12th carbon 12

Question 5

What is relative formula mass ?

Extra bit

Answer 5

The mass of a formula unit compared to the mass of 1/12th carbon 12

• this is the mass of empirical formula only!

Question 6

What is water of crystallisation ?

What happens when no water

Answer 6

Where water molecules are part of a crystalline structure, making it hydrated , otherwise anhydrous

Question 7

What assumptions made in water of crystallisation practical?

Answer 7

1) all the water has been lost, here heat until you get constant mass
2) no further decomposition has happened : many salts decompose further when heated ,
- like your copper sulfate could become black copper oxide , meaning some product can be lost or changed…

Question 8

Some liquid conversions

Answer 8

1cm3 = 1 ml
1dm3 = 1000cm3 = 1000ml = 1 L

Question 9

What is concentration

Answer 9

N= C x V
C= N/ v, mol/ volume in dm3
Thus concentration is the mol of solute per every dm3

To get from moldm-3 to gmol, multiply by formula mass

Question 10

What is a standard solution

HOW TO MAKE!

Answer 10

A solution of known concentration

1) measure exact mass in weighing boat
2) transfer to 100cm3 beaker, rinsing weighing boat in
3) add enough distilled water so it dissolves , stir with glass rod
4) transfer to 250cm3 volumetric flask, and rinse the beaker and funnel in
5) reach the graduation line DROP BY DROP, if go over, ruin whole concentration and restart, this is BOTTOM OF THE MENISCUS .
6) NOW INVERT SEVERAL TIMES or it won’t be CONSISTENT

Question 11

What is molar gas volume
What is room temperature
What is equation linking it to moles

Answer 11

= the volume per mole of gas occupied at a stated temperature and pressure
Eg 24dm3 at rtp
Rtp= 20° and 100kpa (101?

Moles = volume / molar gas volume

Question 12

What are the assumptions made for an ideal gas ?

LEARN =4

Answer 12

• move in random motion
• have ELASTIC COLLISIONS
• size is NEGLIGIBLE
• no INTERMOLECULAR FORCES!

Question 13

What is ideal gas equation ?

What are units (gas constant and VOLUME!)

Answer 13

pV = nRat

P= pressure pascals 
V = volume in m3
N = mol
R= gas constant = 8.314 JMol-1K-1
T = temperature in Kelvin

Question 14

Unit conversions?

Answer 14

M3 to cm3, well 100x100x100 so cm3 to m3 is x 10-6

2) dm3 to m3, dm = 10cm, m = 100, so multiply by 10x10x10 which is 1000, 10x-3 (1000x1000= 1000000)
3) 0k = -273 °, so 0°= 273 k

Question 15

In questions talking about molar volume, what can you take?

Answer 15

Volume = that and mol = 1

Question 16

Why may a reaction not go to completion and affect percentage yield?

Answer 16

• reaction ,as not have gone to completion (reversible reaction means not all of the reactants reacted)
• other side reactions may have taken place alongside main reaction not giving amount of products
• purification of the product and transferring products may result in loss of product

Question 17

Which reactions will give good and bad atom economies

Answer 17

Addition = 100%, condensation = decent

Substation and elimination = bad

Question 18

What do high atom economies give

Answer 18

• a large proportion of desired products and few unwanted waste products
• are important for susuatoanbility as make best use of NATURAL RESOURCES

Question 19

What does improving atom economies do for the environment and industry ?

Answer 19

• makes industrial processes more efficient
• preserves raw materials
• reduces waste

Question 20

What other things need to be considered other than atom economies

• climate
• how sustainable
• good but not efficient?

Answer 20

• for example undesired product is bad like co2, even worse as this affected climate change

In terms of sustainable

• readily available reactants , like carbon and water = SUSTAINABLE
• even though other reactions have high atom economies, will have poor percentage yields, NEED TO CONSIDER THIS WHEN TRYNA FIND BEST EFFICIENT

Question 21

What 3 ways to measure gas volumes ?

Answer 21

@) gas syringe

2) collect over water , upturned cylinder / buret
3) weighing scale for difference of mass

Question 22

What even is atom economy?

How is it different to percentage yield?

Answer 22

A measure of how well atoms have been utilised

• percentage yield as actual, as affected by experiment, atom economy theoretical completely

Question 23

How to increase atom economy ?

What happens when acid and metal mix

Answer 23

Waste product, find other way
2). Bubbles and solid dissolves
X = water of cyrtslsissfion

Question 24

What is the mole

Answer 24

The mole is the number of entities in each mole of cabrin 12
This is equal to avagadros constant