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Chemistry > 2.4 GROUP 2 > Flashcards

2.4 GROUP 2 Flashcards

to learn the trends

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1
Q

solubility of G2 hydroxides

A

solubility trend: increases

Mg( OH )2 insoluble
Ca( OH )2 slightly soluble
*the above have ionic eq

Sr(OH)2 soluble
Ba(OH)2 soluble

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2
Q

solubility of G2 sulfates

A

solubility trend: decreases

MgSO4 soluble

CaSO4 slightly soluble
SrSO4 insoluble
BaSO4 insoluble
*the above have ionic eq

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3
Q

solubility trend of G1 hydroxides and sulfates

A

no trends

because all soluble

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4
Q

why group 1 and 2 metals are called as s block elements?

A

as the highest occupied energy level is the s-orbital

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5
Q

trend in first ionization energy of G2

A

trend: decreases

explanation:
down the group, the proton increases but the shielding effect of inner shells electrons increases too.
however, the outer shell electron is further away from nucleus.
which weakens the force of attraction and less energy is needed to remove an electron

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6
Q

trends down G2

melting point
electrical conductivity
reducing power
reactivity

A

melting point: decreases, weaker metallic bond

electrical conductivity: increases, easier to form delocalised electrons

reducing power: increases , ionisation energy decreases easier to lose electron and from cation

reactivity : increases , easier to form cation

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7
Q

group 2 + oxygen

A

form oxides

refer note

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8
Q

group 2 + water

A

form hydroxides

refer note

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9
Q

group 2 + chlorine

A

form chlorides

refer note

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10
Q

state the acid-base nature of G2 oxides

A

basic oxides
except BeO is amphoteric

non metal oxides are acidic like CO2, NO2

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11
Q

unlike magnesium why barium is kept immersed under paraffin oil or in vacuum sealed ampoules

A

barium is very reactive
readily react with O2 and moisture in air
turns into liquid when exposed to air

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12
Q

lithium chloride can be made by burning lithium in chlorine. why rubidium chloride is not prepared like that

A

rubidium is more reactive

is vigorous and therefore dangerous

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13
Q

bonding present in BeCl2

A

covalent

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14
Q

bonding present in BaCl2

A

ionic

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15
Q

why the type of bonding is different for BeCl2 and BaCl2

A

BeCl2
Be 2+ is small and highly polarising and therefore greater distortion of electron clouds on chlorides
hence, shows greater covalent character

BaCl2
large electronegativity difference between Ba and Cl2
hence shows greater ionic character

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16
Q

compare the reaction of g2 hydroxides and and oxides

A

see notes pg4

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17
Q

how to make metal hydroxides give three ways

A

g2 plus water
g2 oxides except Beo plus water
g2 salt plus base like NaOH

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18
Q

which g2 sulfates is least soluble

A

BaO4

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19
Q

state the use of insolubility of sulfates in medical field and lab test

A

refer to notes pg5

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20
Q

why strontium stops reacting with dilute sulphuric acid after a few seconds even though they react initially

A

strontium and sulphuric acid forms insoluble strontium sulphate. forms a layer around the Sr metal prevent further reaction with acid

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21
Q

barium with cold water

A

barium hydroxide (aq) plus hydrogen

22
Q

aqueous solution of barium hydroxides to a pure sample of barium sulphate

A

barium hydroxides react with excess sulphuric acid to ensure all barium hydroxide convert completely to BaSO4

filter the solution using filter paper

soild obtain is pure barium sulphate

wash

pat dry do not heat cause g2 decompose under heat

23
Q

Mg(Cl)2 + excess NaOH

all aq

A

percipitation
ionic eq form

white percipitate is form
insoluble in excess NaOH
not amphoteric

24
Q

Ba(Cl)2 + excess NaOH

all aq

A

no ionic eq
no percipitate
remains clear

25
Q 
flame test 
Li+
Na+
K+
Rb+
Ca+
Sr+
Ba+
A

Li+ deep red

Na+ golden yellow

K+ lilac

Rb+ bluish red

Ca+ brick red

Sr+ crimson red

Ba+ green

26
Q

flame test method

A

refer notes

27
Q

explanation for flame colour

A

refer notes

28
Q

why platinum or nichrome wire is used in flame test

A

unreactive with conc HCL it is dipped in

will not give a flame colour of its own

29
Q

why conc HCL is used not H2SO4 and HNO3

A

reacts with salt and forms metal chlorides

chlorides are much mire volatile than sulfates or nitrate

30
Q

why is it necessary to clean the wire by repeatedly dipping in conc HCL and heat prior testing

A

to ensure no traces of metal ions remain

that would produce a flame colour which lead to false observation

31
Q

why is it impossible to identify K+ ions in a sample contaminated with small amounts of Na +

A

the intense yellow flame will mask the pale lilac flame

32
Q

thermal decomposition

meaning

A

use of heat to break down a single reactant into 2 or more simpler products

the higher the thermal stability, the higher the temp needed to decompose it

33
Q

g1 carbonates

effect of heat
general eq
trend in thermal stability

A

effect of heat: do not decompose

general eq: no

trend in thermal stability: very stable

34
Q

g2 carbonates

effect of heat
general eq
trend in thermal stability

A

effect of heat: decompose to give metal oxide and co2

general eq: refer notes

trend in thermal stability: increases

35
Q

does g1 hydrogencarbonates decomposes under heat?

A

yes

eq refer notes

36
Q

experiment diagram to investigate thermal stability

A

refer notes pg 8

37
Q

how experiment for thermal stability helps to explain thermal stability

A

time taken foe lime water to turn cloudy

38
Q

experiment diagram to investigate thermal stability

how you would control the factors in the experiment so diff carbonates can be compare

A
  1. constant bunsen flame
    2.fixed height of test tube above flame
  2. fixed moles or mass of carbonates
  3. fixed volume of limewater
    same cloudiness of limewater
39
Q

experiment diagram to investigate thermal stability

this experiment gives only approximate results
suggest an alternative improvement to increase the reliability

A

collect and measure the volume of co2 using a syringe for a fixed Heating time

weigh the solid before and after heating to determine the change in mass or a fixed amount of heating time

40
Q

g1 nitates

effect of heat
general eq
trend in thermal stability
experimental evidence

A

effect of heat: decompose to give metal nitrate and o2

general eq : refer notes pg 9

trend in thermal stability: increases

experimental evidence: time taken for the solid to melt

41
Q

g2 nitates

effect of heat
general eq
trend in thermal stability
experimental evidence

A

effect of heat: decompose to give metal oxide, nitrogen dioxide amd o2

general eq: refer notes

trend in thermal stability: increases

experimental evidence: time taken for appearance of brown gas and time taken for solid to melt

42
Q

the thermal stability of ionic compounds depends on

A

ionic charge of cation

ionic radius of cation

43
Q

down g2 carbonates and nitrate increases because

A

cation radius increases but charge remains the same

polarising power of cation decreases

difficult to distort electron cloud on anion / more energy is needed to weaken the bond

44
Q

why MgO2 cannot be further decomposed to Mg and O2?

A

O2- is small and high charge

there fore O2- cannot be easily polarised

45
Q

why G1 carbonates are more stable than G2 carbonates

A

g1 metal ion is less polarising than g2 metal ion

less distortion of electron cloud on CO3 2-

more energy is needed to break the bond in g1 carbonates

46
Q

calcium plus water

A

calcium hydroxide and hydrogen

47
Q

state the trend in solubilty of g2 hydroxides

A

increases

48
Q

why MgCl2 does not produce a flame colour

A

the radiation is not in the visible light range

49
Q

polarising power

meaning

A

the ability of cation to distort the electron cloud of cation

50
Q

radium hydroxide soluble in water?

A

yes

51
Q

radium sulphate soluble in water?

A

no

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