quantitative and qualitative chemistry

Question 1

Avogadro’s constant

Answer 1

the number of particles in 1 mole = 6 × 10^23 mol−1

Question 2

conversion of tonnes to kg and g

Answer 2

1 tonne = 1000kg = 1,000,000g

Question 3

empirical formula

Answer 3

• the simplest whole number ratio of atoms of each element present in a compound
• can be determined from the % composition of mass of the elements present in the compound
• formula: (mass or %mass / Mr) for both elements, then simplify ratio

Question 4

molecular formula from empirical formula

Answer 4

do Mr of molecular formula / Mr of empirical formula, then multiply empirical formula by answer

Question 5

molar volume of gases at room temp and pressure

Answer 5

24lmol-1

Question 6

formula for mass of solute

Answer 6

mass of solute (in g) = conc. (in gL-1) x volume (in L)

Question 7

relationship between temp and solubility

Answer 7

• as temp increases, solubility of salts increases

- as temp increases, solubility of gases decreases

Question 8

%yield =

Answer 8

(actual yield / theoretical yield) x 100

Question 9

why is it not always possible to obtain the theoretical mass of a product

Answer 9

• the reaction will not go to completion if it is reversible
• some of the product may be lost when it is separated from the reaction mixture
• some of the reactants may also react in ways different to the expected reaction

Question 10

1 dm3 (dm cubed) =

Answer 10

1 litre

Question 11

test for hydrogen gas

Answer 11

-hydrogen burns with a squeaky pop

Question 12

test for oxygen gas

Answer 12

-oxygen relights a glowing splint

Question 13

test for carbon dioxide gas

Answer 13

• carbon dioxide turns limewater cloudy

- this is due to the insoluble suspension of calcium carbonate (precipitate) formed

Question 14

reactivity series

Answer 14

• potassium PETER
• sodium SMITH
• lithium LUCKILY
• calcium CAUGHT
• magnesium MY
• aluminium AUNT
• carbon CATHERINE
• zinc ZINA
• iron IN
• tin THE
• lead LARDER
• hydrogen HIDDEN
• copper CAREFULLY
• mercury MUNCHING
• silver SOME
• gold GREEN
• platinum PEAS

Question 15

test for chlorine gas

Answer 15

-litmus (pH) paper turns red then white

Question 16

flame tests
Li =
Na=
K=
Ca=
Cu=

Answer 16

• Li – crimson red
• Na – yellow-orange
• K – lilac
• Ca – red-orange
• Cu – green

Question 17

concentration formula

Answer 17

conc = (mass of solute in grams) / (volume of solution in litres)

Question 18

1 decilitre (dL) =

Answer 18

100ml / 0.1L

Question 19

test for halide ions (Cl-, B-, I-)

Answer 19

• add dilute nitric acid and a few drops of silver nitrate solution to the unknown solution
• halide ions will precipitate as silver halides
• each silver halide precipitate has a distinctive colour:
  
  • silver iodide = yellow
  • silver bromide = cream
  • silver chloride = white

Question 20

test for sulfate ions

Answer 20

• addition of dilute HNO3 / HCl to the unknown solution, followed by a solution of barium nitrate/chloride
• a white precipitate indicates the presence of sulfate ions.

Question 21

test for carbonate ions

Answer 21

-carbonate ions react with an acid to release CO2 gas

Question 22

order of tests for anions

Answer 22

If the anions present in a sample is unknown, test in this specific order:

1) carbonate ions
2) sulfate ions
3) halide ions

Question 23

flame tests (testing for cations)

Answer 23

• thin wire is washed in a little acid, then dipped into the unknown substance
• wire is placed in the blue flame of a Bunsen burner
  lithium: crimson red
  sodium: yellow-orange
  potassium: lilac
  calcium: red-orange
  copper: green

Question 24

test for water

Answer 24

-copper(II) sulfate solid is white when anhydrous but blue when hydrated

Question 25

1m3 =

Answer 25

1000litres

Question 26

iron colours

Answer 26

Fe2+  = green
Fe3+  = orange-brown

Question 27

lead valency

Answer 27

+2

Question 28

zinc valency

Answer 28

+2