inorganic chemistry and the periodic table

Question 1

what is first ionisation enthalpy?

Answer 1

the enthalpy change that occurs when one mole of electrons is removed from one mole of gaseous atoms

Question 2

why does first ionisation enthalpy increase as we move across a period?

Answer 2

the number of protons in the nucleus increases which increases the nuclear charge and the amount of energy required to remove them

Question 3

formula of a nitrate ion

Answer 3

NO3-

Question 4

formula of a sulphate ion

Answer 4

SO4^2-

Question 5

formula of a carbonate ion

Answer 5

CO3^2-

Question 6

formula of a hydroxide ion

Answer 6

OH-

Question 7

formula of an ammonium ion

Answer 7

NH4+

Question 8

formula of a hydrogencarbonate ion

Answer 8

HCO3-

Question 9

formula of a copper ion

Answer 9

Cu2+

Question 10

formula of a zinc ion

Answer 10

Zn2+

Question 11

formula of a lead ion

Answer 11

Pb2+

Question 12

formula of an iron (II) ion

Answer 12

Fe2+

Question 13

formula of a iron (III) ion

Answer 13

Fe3+

Question 14

why does ionisation energy decrease down a group?

Answer 14

the number of shells in the atom increases, which increased the shielding of the outer electrons from the nucleus.
the nuclear radius also increases.
both these mean the attractive nuclear force felt by the electron is smaller, so it takes less energy to remove outer electrons

Question 15

how do the charge densities of group 2 ions affect the thermal stability of their carbonates?

Answer 15

smaller ions with the same charge have higher charge densities and distort the carbonate ion, so that the compound will decompose at a lower temperature

Question 16

how can we test for Fe2+ ions?

Answer 16

add OH- ions, the green solution will form a green precipitate

Question 17

how can we test for Fe3+ ions?

Answer 17

ass OH- ions, the yellow solution will form an orange precipitate

Question 18

how can we test for Cu2+ ions?

Answer 18

add OH- ions, the blue solution will form a blue precipitate

Question 19

how can we test for NH4+ ions?

Answer 19

add NaOH to a boiling tube containing the NH4+ ions, warm the boiling tube, hold damp red litmus paper at the mouth.
=> blue if NH4+ present

Question 20

how can we test for Al3+ ions?

Answer 20

add OH- ions, the colourless solution will form a white precipitate

Question 21

how can we test for Cl- ions?

Answer 21

add HNO3, shake, add a few drops of AgNO3.
Cl- => white ppt

Question 22

how can we test for Br- ions?

Answer 22

add HNO3, shake, add a few drops of AgNO3
Br- => cream ppt

Question 23

how can we test for I- ions?

Answer 23

add a few drops of HNO3, shake, add a few drops of AgNO3
I- => yellow ppt

Question 24

how can we test for SO4^2- ions?

Answer 24

add Ba2+ ions, a white ppt will form

Question 25

how can we test for CO3^2- ions?

Answer 25

add dilute nitric acid, if effervescence occurs then CO3^2- ions are present

Question 26

ion flame test colours

Answer 26

Na+ = orange Ca+ = brick red Li+ = red K+ = lilac Ba2+ = green Cu2+ = blue-green

Question 27

how can we test for Pb2+ ions?

Answer 27

add OH- ions, a white ppt will form