What are electrophiles and nucleophiles? Explain with examples.
An electrophile is a reagent that takes away an electron pair. In other words, an electron-seeking reagent is called an electrophile (E+). Electrophiles are electron-deficient and receiver of an electron pair.
Carbocations and (CH3CH+2) neutral molecules having functional groups such as carbonyl group are examples of electrophiles.
A nulceophile is a reagent that brings an electron pair. In other words, a nucleus-seeking reagent is called a nulceophile (Nu:).
For example: OH-, NC-, carbanions (R3C-), etc.
Neutral molecules such as H2ö and ammonia also act as nulceophiles because of the presence of a lone pair.
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?
The unpaired electrons in Al and Si are present in 3p orbital. Which electrons will experience more effective nuclear charge from the nucleus?
Give the number of electrons in the species , H2 and
The ionization constant of nitrous acid is 4.5 x 10-4. Calculate the pH of 0.04 M sodium nitrite solution and also its degree of hydrolysis.
Discuss the principle of estimation of halogens, sulphur and phosphorus present in an organic compound.
Saline hydrides are known to react with water violently producing fire. Can CO2, a well known fire extinguisher, be used in this case? Explain.
Do you expect different products in solution when aluminium(III) chloride and potassium chloride treated separately with
(i) normal water
(ii) acidified water, and
(iii) alkaline water?
Write equations wherever necessary.
Discuss the general characteristics and gradation in properties of alkaline earth metals.
An element with mass number 81 contains 31.7% more neutrons as compared to protons. Assign the atomic symbol.
Explain why is there a phenomenal decrease in ionisation enthalpy from carbon to silicon?
Indicate the σ and π bonds in the following molecules :
(i) C6H6,
(ii) C6H12,
(iii) CH2Cl2,
(iv) CH2=C=CH2,
(v) CH3NO2,
(vi) HCONHCH3