Quantative Chemstry

Question 1

1 mole

Answer 1

• mol

- Avagadro number of particles in a substance

Question 2

Avagadros number

Answer 2

• one mol

- 6.02x 10^23 atoms

Question 3

Mol

Answer 3

Mass/mr

Question 4

Atomic number

Answer 4

Number of protons or electrons

Question 5

Mass number

Answer 5

Number of protons and neutrons

Question 6

Isotypes

Answer 6

• Atoms of the same element
• same atomic number- same number of protons
• diff no. Neutrons (diff mass number)

Question 7

How to calculate mass of product/reactant of reaction

Answer 7

• balanced equation
• find ratio between products/reactants
• find mr of chemicals interested in
• calculate no. Mole from chemical given mass
• use ratio to calculate no. Mol in other chemicals
• calculate mas from mol

Question 8

How to balance equations from given masses

Answer 8

• calculate mol from given mass
• divide : no mol of each substance/smallest no of mol in reaction
• make ratio from this
• implement into balanced symbol equation

Question 9

Limiting reactant

Answer 9

• in a chemical reaction w/ two reactants, common to use an excss of one of the reactants to ensure all of the other is used
• reactant that is completely used up is the. Limiting reactant
• limits amount of product that can be made
• amount of product fromed is directly proportional to amount of limiting reactant

Question 10

Relative formula mass (definition)

Answer 10

Sum of relative atomic masses of the atoms in the numbers shown in the formula
-mr

Question 11

Relative atomic mass

Answer 11

• average mass of all diff isotypes of an element
• ar
• (ar x abundance)/number of isotypes(100)

Question 12

Atom “ economy

Answer 12

Mr of desired product x 100 / mr of all reactants

Question 13

Percentage purity

Answer 13

Mass of pure product x 100/ actual mass

Question 14

Concentration

Answer 14

• amount of mol of solute in a given volume of solution

- mol/dm3

Question 15

Volume of gas - at 20C and 1atm

Answer 15

24 x mol

Question 16

How to find the conc of other solution

Answer 16

• find mol of other solution:
  
  • mol=conc x vol
  • use ratio to find mol of other solution

Question 17

Standard solution

Answer 17

Has an accurately known conc

Question 18

Percentage yield

Answer 18

Actual mass of product x 100 / max mass of product

Question 19

0% percentage yield

Answer 19

No product made

Question 20

Why is percentage yield not 100%

Answer 20

• reaction may not go to completion because its REVERSABLE
• some of product may be lost when its SEPERATED from the reaction mixture
• may react in a diff way to expected reaction
• evaporation
• not all reactants react to make products

Question 21

How to find percentage yield

Answer 21

• find mr
• work out mass theoretical mass
  
  • Mr x n of molecules eg. 2Cl = x2
  • divide this number by no. Mr of reactants
  • times result by theoretical mass eg. 50g = x50
• use formula

Question 22

Percentage by mass

Answer 22

Mr of element x 100 /mr of compound

Question 23

Converting from mol/dm3 -> g/dm3

Answer 23

Conc (mol/dm3) x mr

Question 24

Molar vol of gases

Answer 24

Equal amounts of moles of gases occupy same volme under same conditions of temp and pressure

Question 25

Mol of gas (equation)

Answer 25

Vol(dm3)/24dm3. = vol(cm3)/24 000cm3

Question 26

How to calculate mass of gas

Answer 26

• calculate no. Of mol
• find molar ratio
• find mol of gas
• find mass =mr x mol =g

Question 27

Atom economy (utilisation)

Answer 27

• measure of amount of starting materials that end u as desirable product
• used for sustainable development
• used for economic reasons -use reactions w/ high atom economy

Question 28

Why is a particular reaction pathway used?

Answer 28

• atom economy
• yield
• rate of reaction
• equilibrium position (how stable/easy to push one way)
• usefulness of by-product
• cost of materials, heat, pressure
• safety (high pressure/toxicity)
• sustainability (crude oil)
• availability
• waste disposal
• pollution
• energy requirements