Assign oxidation number to the underlined elements in each of the following species:
(a) NaH2PO4
(b) NaHSO4
(c) H4P2O7
(d) K2MnO4
(e) CaO2
(f) NaBH4
(g) H2S2O7
(h) KAl(SO4)2.12 H2O
(a) NaH2PO4
Let's assume oxidation number of P is x.
We know that,
Oxidation number of Na = +1
Oxidation number of H = +1
Oxidation number of O = -2
Then we have
1(+1) + 2(+1) + 1 (x) + 4(-2) = 0
⇒ 1 + 2 + x - 8 = 0
⇒ x - 5 = 0
⇒ x = + 5
Hence, oxidation number of P is +5
(b) NaHSO4
Let's assume oxidation number of S is x.
Oxidation number of Na = +1
Oxidation number of H = +1
Oxidation number of O = -2
Then we have:
1(+1) + 1(+1) + 1 (x) + 4(-2) = 0
⇒ 1 + 1 + x - 8 = 0
⇒ x-6 = 0
⇒ x = +6
Hence, oxidation number of S is +6
(c) H4P2O7
Let's assume oxidation number of P is x.
Oxidation number of H = +1
Oxidation number of O = -2
Then we have:
4(+1) + 2(x) + 7 (-2) = 0
⇒ 4 + 2x - 14 = 0
⇒ 2x - 10 = 0
⇒ 2x = +10
⇒ x = +5
Hence, Oxidation number of P is +5
(d) K2MnO4
Let's assume oxidation number of Mn is x.
Oxidation number of K = +1
Oxidation number of O = -2
Then we have:
2(+1) + 1(x) + 4 (-2) = 0
⇒ 2 + x - 8 = 0
⇒ x - 6 = 0
⇒ x = +6
Hence, Oxidation number of Mn is +6
(e) CaO2
Let's assume oxidation number of O is x.
Oxidation number of Ca = +2
Then we have:
1(+2) + 2(x) = 0
⇒ 2 + 2x = 0
⇒ 2x = -2
⇒ x = -1
Hence, Oxidation number of O is -1
(f) NaBH4
Let's assume oxidation number of B is x.
Oxidation number of Na = +1
Oxidation number of H = -1
Then we have:
1(+1) + 1(x) + 4(-1) = 0
⇒ 1 + x -4 = 0
⇒ x - 3 = 0
⇒ x = +3
Hence, Oxidation number of B is +3.
(g) H2S2O7
Let's assume oxidation number of S is x.
Oxidation number of O = -2
Oxidation number of H = +1
Then we have:
2(+1) + 2(x) + 7(-2) = 0
⇒ 2 + 2x - 14 = 0
⇒ 2x - 12 = 0
⇒ x = +6
Hence, Oxidation number of S is +6.
(h) KAl(SO4)2.12 H2O
Let's assume oxidation number of S is x.
Oxidation number of K = +1
Oxidation number of Al = +3
Oxidation number of O = -2
Oxidation number of H = +1
Then we have:
1(+1) + 1 (+3) + 2(x) + 8(-2) + 24(+1) + 12 (-2) = 0
⇒ 1 + 3 + 2x -16 +24 -24 = 0
⇒ 2x - 12 = 0
⇒ 2x = +12
⇒ x = +6
Hence, Oxidation number of S is +6.
Balance the following redox reactions by ion – electron method :
(a) MnO4 – (aq) + I – (aq) → MnO2 (s) + I2(s) (in basic medium)
(b) MnO4 – (aq) + SO2 (g) → Mn2+ (aq) + HSO4– (aq) (in acidic solution)
(c) H2O2 (aq) + Fe 2+ (aq) → Fe3+ (aq) + H2O (l) (in acidic solution)
(d) Cr2O7 2– + SO2(g) → Cr3+ (aq) + SO42– (aq) (in acidic solution)
What are the oxidation number of the underlined elements in each of the following and how do you rationalise your results ?
(a) KI3
(b) H2S4O6
(c) Fe3O4
(d) CH3CH2OH
(e) CH3COOH
Justify that the following reactions are redox reactions:
(a) CuO(s) + H2(g) → Cu(s) + H2O(g)
(b) Fe2O3(s) + 3CO(g) → 2Fe(s) + 3CO2(g)
(c) 4BCl3(g) + 3LiAlH4(s) → 2B2H6(g) + 3LiCl(s) + 3 AlCl3 (s)
(d) 2K(s) + F2(g) → 2K+F– (s)
(e) 4 NH3(g) + 5 O2(g) → 4NO(g) + 6H2O(g)
Balance the following equations in basic medium by ion-electron method and oxidation number methods and identify the oxidising agent and the reducing agent.
(a) P4(s) + OH – (aq) → PH3(g) + HPO2 – (aq)
(b) N2H4(l) + ClO3 – (aq) → NO(g) + Cl–(g)
(c) Cl2O7 (g) + H2O2(aq) → ClO – 2(aq) + O2(g) + H + (aq)
Fluorine reacts with ice and results in the change:
H2O(s) + F2(g) → HF(g) + HOF(g)
Justify that this reaction is a redox reaction.
Write the formulae for the following compounds:
(a) Mercury(II) chloride
(b) Nickel(II) sulphate
(c) Tin(IV) oxide
(d) Thallium(I) sulphate
(e) Iron(III) sulphate
(f) Chromium(III) oxide
While sulphur dioxide and hydrogen peroxide can act as oxidising as well as reducing agents in their reactions, ozone and nitric acid act only as oxidants. Why?
Identify the substance oxidised, reduced, oxidising agent and reducing agent for each of the following reactions:
(a) 2AgBr (s) + C6H6O2(aq) → 2Ag(s) + 2HBr (aq) + C6H4O2(aq)
(b) HCHO(l) + 2[Ag (NH3)2]+(aq) + 3OH-(aq) → 2Ag(s) + HCOO-(aq) + 4NH3(aq) + 2H2O(l)
(c) HCHO (l) + 2Cu2+(aq) + 5 OH-(aq) → Cu2O(s) + HCOO-(aq) + 3H2O(l)
(d) N2H4(l) + 2H2O2(l) → N2(g) + 4H2O(l)
(e) Pb(s) + PbO2(s) + 2H2SO4(aq) → 2PbSO4(s) + 2H2O(l)
The compound AgF2 is an unstable compound. However, if formed, the compound acts as a very strong oxidizing agent. Why?
Calculate the oxidation number of sulphur, chromium and nitrogen in H2SO5, Cr2O2- 7 and NO– 3. Suggest structure of these compounds. Count for the fallacy.
How do you account for the formation of ethane during chlorination of methane?
What are hybridisation states of each carbon atom in the following compounds ?
(i) CH2=C=O,
(ii) CH3CH=CH2,
(iii) (CH3)2CO,
(iv) CH2=CHCN,
(v) C6H6
What will be the minimum pressure required to compress 500 dm3 of air at 1 bar to 200 dm3 at 30°C?
What are the common physical and chemical features of alkali metals?
Calculate the molecular mass of the following:
(i) H2O
(ii) CO2
(iii) CH4
What is the basic theme of organisation in the periodic table?
Explain the formation of a chemical bond.
Choose the correct answer. A thermodynamic state function is a quantity
(i) used to determine heat changes
(ii) whose value is independent of path
(iii) used to determine pressure volume work
(iv) whose value depends on temperature only.
A liquid is in equilibrium with its vapour in a sealed container at a fixed temperature. The volume of the container is suddenly increased.
a) What is the initial effect of the change on vapour pressure?
b) How do rates of evaporation and condensation change initially?
c) What happens when equilibrium is restored finally and what will be the final vapour pressure?
Justify the position of hydrogen in the periodic table on the basis of its electronic configuration.
Calculate the total pressure in a mixture of 8 g of dioxygen and 4 g of dihydrogen confined in a vessel of 1 dm3 at 27°C. R = 0.083 bar dm3 K–1 mol–1.
Emission transitions in the Paschen series end at orbit n = 3 and start from orbit n and can be represented as v = 3.29 × 1015 (Hz) [1/32 – 1/n2]
Calculate the value of n if the transition is observed at 1285 nm. Find the region of the spectrum.
Using the equation of state pV = nRT; show that at a given temperature density of a gas is proportional to gas pressurep.
Suggest a reason as to why CO is poisonous.
Pressure is determined as force per unit area of the surface. The SI unit of pressure, Pascal is as shown below:
1Pa = 1N m–2
If mass of air at sea level is 1034 g cm–2, calculate the pressure in Pascal.
Determine the empirical formula of an oxide of iron which has 69.9% iron and 30.1% dioxygen by mass.
Give the number of electrons in the species , H2 and
Compare the relative stability of the following species and indicate their magnetic properties:
O2,O2+,O2- (superoxide), O22-(peroxide)
Given
N2(g) + 3H2(g) → 2NH3(g) ; ΔrH0 = –92.4 kJ mol–1
What is the standard enthalpy of formation of NH3 gas?
Calcium carbonate reacts with aqueous HCl to give CaCl2 and CO2 according to the reaction,
CaCO3(s) + 2 HCl(aq) → CaCl2(aq) + CO2(g) + H2O(l)
What mass of CaCO3 is required to react completely with 25 mL of 0.75 M HCl?
Gud to disclose all the answers .anyway thanks