S-Block Flashcards

Question

alkali metals properties?

Answer 1

silvery white, soft metals, highly reactive, strong reducing agents

Answer 2

minerals/electrolytes in human body; blood pressure regulation, action potentials for nerve cells NaCl for seasoning

Answer 3

carbonates, acetates, citrate treatments for manic-depressive psychoses (bipolar disorder) as a mood stabiliser

Answer 4

atomic radius increases ionisation energy decreases mp and bp decreases weak metallic bonding between atoms density increases (but got low density) enthalpy of sublimation decreases (turn to gas phase)

Answer 5

Li and Na prepared by electrolysis of their molten salts by DOWNS process electrolysis of molten NaCl at 600ºC and 4-8 eV

Answer 6

2 NaCl (l)  2 Na (l) + Cl2 (g)

Answer 7

>50% CaCl2 additives to keep the salt liquid below the NaCl melting point of 801°C; Ca2+ is more difficult to reduce than Na+, a carbon anode and an iron cathode are used

Answer 8

K+ and Na+ stored under oil, as reactive in oxygen K+ cannot be prepared by electrolysis (too reactive) Na + KCl --> NaCl + K at high temp, to drive equilibrium in substitution reaction

Answer 9

heavier alkali metals are more reducing than the lighter ones

Answer 10

synthesis of tetraethyl leads as a fuel additive for anti knocking properties 4 NaPb + 4 EtCl → PbEt4 + 3 Pb + 4 NaCl released alot of lead into the atmosphere

Answer 11

Na, K and Na/K with water can be used to dry chemicals effectively. Using a metal that will be liquid at the solvents boiling point, can reflux under inert gas and distil away the solvent

Answer 12

4 Li + O2 → 2 Li2O (oxide, O2-) 2 Na + O2 → Na2O2 (peroxide, O22-, with O-O single bond) 5 K + O2 → KO2 (superoxide, O2 *-, radical anion) this is very unstable

Answer 13

KO2 is a superoxide. yellow, paramagnetic and shock sensitive

Answer 14

4 KO2 (s) + 2 H2O (l) → 4 K+ (aq) + 4 OH- (aq) + 3 O2 HO2 is not stable due to disproportionationation and gives O2 hence needs to be kept in inert gas

Answer 15

4 KO2 + 2 CO2 → 2 K2CO3 + 3 O2; 4 KO2 + 4 CO2 + 2 H2O → 4 KHCO3 + 3 O2. O2 is released so they can be called oxygen generators in space suits

Answer 16

6 Li (s) + N2 (g) = 2 Li3N (s) has to be stored under argon forms strong triple bonds Li+ able to form stable lattice with N3- anions. cannot be done with larger anions, overcoming disassociation energy N3- is hard and small and this needs to be balanced by also small metals ie 3x Li+1

Answer 17

react violently (exothermic) 2 M (s) + 2 H2O (l) -> 2 MOH (aq) + H2 (g) more reactive down the group as Heavier metals quickly melt with the heat of the reaction, this melting causes new metal surface to be exposed and accelerates the reaction

Answer 18

Na/K alloy is liquid at and below room temperature. Na/K alloy (40-90 weight % K): large liquid range (-13°C to +785°C for 77% K; ca. K2Na) Na/K is sometimes used as a liquid coolant in nuclear facilities (e.g. experimental nuclear reactors)! The alloy has a good thermal conductivity.

Answer 19

alkali metals with graphites, graphites are reduced and M+ cations intercalate and coordinate to 6 membered rings between the graphite layers (expanding to fit) these are strong reducing agents

Answer 20

gives bronze- coloured highly reactive intercalation compound. KC8 is a strong reducing agent. It is a powder that can be readily handled under dry inert gas. It is pyrophoric and in air spontaneously bursts into flames.

Answer 21

formula: LiC6 negative anode LiC6 → Li+ + “C6” + e- positive cathode CoO2 + Li+ + e- → LiCoO2 used in rechargeable batteries. The small Li+ can migrate; moves in and out of the solid structures (“C” and CoO2)  a reversible system that can be recharged (the opposite reactions). an electrolyte, e.g. LiPF6 in an organic (non-protic) solvent such as diethyl carbonate, and separator diaphragm (permeable for Li+)

Answer 22

Na + H2O = NaOH + H2

Answer 23

NaCl = NaOH + Cl2 and H2 (chloralkali process) NaCl is able to be mined or obtained by evaporation of seawater

Answer 24

Alkali metals + halogens = MX salts (colourless and ionic), in an exothermic reaction

Answer 25

alkali metals hydroxide/carbonates + hydrohalic acid (HX) = salt + water (+carbon dioxide) Li2CO3 (aq) + 2 HBr (aq) → 2 LiBr (aq) + H2O (l) + CO2 (g)

Answer 26

are water soluble, except LiF cause it is sparingly soluble due to large lattice energy (2x small hard ions) which is not overcome by hydration enthalpy and has the largest lattice energy, which not offset by enthalpy of hydration

Answer 27

Liquid metal + hydrogen gas = Alkali metal hydrides these are ionic due to EN difference 2 M + H2 → 2 MH

Answer 28

Reactivity. LiH < NaH < KH with KH more of a mismatched ion pair and less lattice energy has to be invested for reactions

Answer 29

exothermic reaction 2 MH + 2 H2O → 2 MOH + H2 comproportionation reaction

Answer 30

elements with two oxidation states converts to a product with element in one oxidation state

Answer 31

NaCl has face centred cubic structure alternating cations and anion, 6 neighbours CsCl, CsBr, Csl has primitive cubic structure. Common for more similarly sized cations and anions, 8 neighbours, ion centre surrounded by 8 opposite charge ions 1:1 ratio

Answer 32

NO3 - (nitrate), SO42- (sulfate), CO32- (carbonate) and PO43- (phosphate)

Answer 33

Solvay process. used in glass industry NaCl +. CaCO3 = Na2CO3

Answer 34

have large polarisable anions (LiI and LiClO4), these are soluble in ethereal solvents (these include diethyl ether Et2O) where there is attraction between lone pairs

Answer 35

central Li corrugated to OEt2 x 4 around in tetrahedral structure

S-Block Flashcards

(61 cards)