Discuss the principle of estimation of halogens, sulphur and phosphorus present in an organic compound.
Estimation of halogens
Halogens are estimated by the Carius method. In this method, a known quantity of organic compound is heated with fuming nitric acid in the presence of silver nitrate, contained in a hard glass tube called the Carius tube, taken in a furnace. Carbon and hydrogen that are present in the compound are oxidized to form CO2 and H2O respectively and the halogen present in the compound is converted to the form of AgX. This AgX is then filtered, washed, dried, and weighed.
Let the mass of organic compound be m g.
Mass of AgX formed = m1 g
1 mol of Agx contains 1 mol of X.
Therefore, Mass of halogen in m1 g of AgX = (Atomic mass of X x m1 g) / (Molecular mass of AgX)
Thus, % of halogen will be = (Atomic mass of X x m1 x 100) / (Molecular mass of AgX x m)
Estimation of Sulphur
In this method, a known quantity of organic compound is heated with either fuming nitric acid or sodium peroxide in a hard glass tube called the Carius tube. Sulphur, present in the compound, is oxidized to form sulphuric acid. On addition of excess of barium chloride to it, the precipitation of barium sulphate takes place. This precipitate is then filtered, washed, dried, and weighed.
Let the mass of organic compound be m g.
Mass of BaSO4 formed = m1 g
1 mol of BaSO4 = 233 g BaSO4 = 32 g of Sulphur
Therefore, m1 g of BaSO4 contains 32 x m1 / 233 g of sulphur
Thus, percentage of sulphur = 32 x m1 x100 / 233 x m
Estimation of phosphorus
In this method, a known quantity of organic compound is heated with fuming nitric acid. Phosphorus, present in the compound, is oxidized to form phosphoric acid. By adding ammonia and ammonium molybdate to the solution, phosphorus can be precipitated as ammonium phosphomolybdate.
Phosphorus can also be estimated by precipitating it as MgNH4PO4 by adding magnesia mixture, which on ignition yields Mg2P2O7.
Let the mass of organic compound be m g.
Mass of ammonium phosphomolybdate formed = m1 g
Molar mass of ammonium phosphomolybdate = 1877 g
Thus, percentage of phosphorus = (31 x m1 x 100 %) / (1877 x m)
If P is estimated as Mg2P2O7,
Then percentage of phosphorus = (62xm1x100%) / (222xm)
The mass of an electron is 9.1 × 10–31 kg. If its K.E. is 3.0 × 10–25 J, calculate its wavelength.
Calculate the amount of carbon dioxide that could be produced when
(i) 1 mole of carbon is burnt in air.
(ii) 1 mole of carbon is burnt in 16 g of dioxygen.
(iii) 2 moles of carbon are burnt in 16 g of dioxygen.
Calculate the wavelength of an electron moving with a velocity of 2.05 × 107 ms–1.
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)
In a process, 701 J of heat is absorbed by a system and 394 J ofwork is done by the system. What is the change in internal energy for the process?
What will be the minimum pressure required to compress 500 dm3 of air at 1 bar to 200 dm3 at 30°C?
In a reaction A + B2 → AB2 Identify the limiting reagent, if any, in the following reaction mixtures.
(i) 300 atoms of A + 200 molecules of B
(ii) 2 mol A + 3 mol B
(iii) 100 atoms of A + 100 molecules of B
(iv) 5 mol A + 2.5 mol B
(v) 2.5 mol A + 5 mol B
At 0°C, the density of a certain oxide of a gas at 2 bar is same as that of dinitrogen at 5 bar. What is the molecular mass of the oxide?
Which one of the following will have largest number of atoms?
(i) 1 g Au (s)
(ii) 1 g Na (s)
(iii) 1 g Li (s)
(iv) 1 g of Cl2(g)
Density of a gas is found to be 5.46 g/dm3 at 27 °C at 2 bar pressure. What will be its density at STP?
How can you explain higher stability of BCl3 as compared to TlCl3?
Identify the functional groups in the following compounds
What is the total number of sigma and pi bonds in the following molecules?
(a) C2H2 (b) C2H4
Considering the elements F, Cl, O and N, the correct order of their chemical reactivity in terms of oxidizing property is:
(a) F > Cl > O > N
(b) F > O > Cl > N
(c) Cl > F > O > N
(d) O > F > N > Cl
What do you mean by ozone hole? What are its consequences?
An ion with mass number 37 possesses one unit of negative charge. If the ion contains 11.1% more neutrons than the electrons, find the symbol of the ion.
The ionization constant of dimethylamine is 5.4 x 10-4. Calculate its degree of ionization in its 0.02 M solution. What percentage of dimethylamine is ionized if the solution is also 0.1 M in NaOH?
What are the common physical and chemical features of alkali metals?
Write the significance/applications of dipole moment.
(a) Classify following oxides as neutral, acidic, basic or amphoteric:
CO, B2O3, SiO2, CO2, Al2O3, PbO2, Tl2O3
(b) Write suitable chemical equations to show their nature.