Lanthanoids

Question 1

Lanthanoids are (Apperarence, hardness, colour)

Answer 1

Silvery, soft, white metals

Question 2

In air reactivity

Answer 2

high, tarnish rapidly

Question 3

Left to Right hardness

Answer 3

increases

Question 4

___ is steel hard

Answer 4

Samarium

Question 5

Melting points range from

Answer 5

1000K to 1200K

Question 6

Samarium melts at

Answer 6

1623K

Question 7

Heat and electricity

Answer 7

Good conductors

Question 8

Structure

Answer 8

Typical metallic structure

Question 9

Density and other properties change smoothly except for

Answer 9

Eu and Yb; Sm and Tm

Question 10

Coloured in solid/aqueous/both

Answer 10

Coloured in both solid and aqueous state

Question 11

Absorption bands are

Answer 11

narrow because of excitation within f level

Question 12

Ionistation 1st and 2nd enthalpy are comparable with those of

Answer 12

Calcium

Question 13

Abnormally low 3rd IE for

Answer 13

Lanthanum, Gadolinium, Lutetium

Question 14

Earlier members of Lanthanoid have reactivity like

Answer 14

Calcium

Question 15

Later members of lanthanoid have reactivity like

Answer 15

Aluminium

Question 16

Ln3+ / Ln values range from

Answer 16

-2.2 to -2.4 V

Question 17

Ln3+/Ln value is abnormal for

Answer 17

Eu; -2V

Question 18

Metals combine with __ when ___

Answer 18

Combine with hydrogen when gently heated in the gas

Question 19

Carbides are formed when

Answer 19

Metals are heated with carbon at 2773 K; Ln2C3, Ln3C, LnC2

Question 20

Reaction of lanthanoids with dilute acids

Answer 20

Liberation of hydrogen

Question 21

Reaction with halogens

Answer 21

Burn in halogen to form halides

Question 22

Hydroxides are

Answer 22

Definite compounds, not just hydrated oxides

Question 23

Lanthanoid metals are

Answer 23

Basic like alkaline earth metals and hydroxides

Question 24

Best use of lanthanoids

Answer 24

Alloy production

Question 25

Misch Metal consists of

Answer 25

95 percent Ce
5 percent Iron
traces of S, C, Ca, and Al

Question 26

Misch metal is used in __ based alloys

Answer 26

Magnesium based alloys to produce bullets, shell, lighter flint

Question 27

Mixed oxides of lanthanoids are used as catalysts in

Answer 27

Petroleum cracking

Question 28

Ln oxides are used as

Answer 28

phosphors in television screens and fluorescing surfaces

Question 29

Assertion : Ce (IV) is a good analytical reagent

Answer 29

Reason: Reaction rate of Ce4/Ce3 is very slow

Question 30

Assertion :Samarium and Europium are similar

Answer 30

Reason: Both exhibit +2 and +3 oxidation states

Question 31

Identical radii, is a consequence of lanthanoid contraction, difficult to separate, occur together in nature

Answer 31

Zr and Hf

Question 32

Lanthanum and actinium

Answer 32

are not f block

Question 33

Lanthanoids resemble one another

Answer 33

More than any other series

Question 34

Assertion: Complications occur in studying actinoids

Answer 34

Reason : Radioacticity and Occurence of wide range of oxidation states