Define hydrogen bond. Is it weaker or stronger than the van der Waals forces?
A hydrogen bond represents a dipolar attraction between hydrogen atom and highly electronegative atom. The hydrogen bond is represented by ----------(dotted lines).
For example: H -----------X -----------X -------- X------
X = O, N, S, F, Cl….
The bond pair involved in hydrogen bonding was attracted more towards highly electronegative atom, as a result H atom will start acquiring a partial positive charge (δ+) and the electronegative atom will acquire a partial negative charge (δ-).
The magnitude of H-bonding is maximum in the solid state and minimum in the gaseous state.
Hydrogen bonds are of two types
(i) Intermolecular H-bond e.g., HF, H2O etc.
(ii) Intramolecular H-bond e.g., o-nitrophenol
Vander waal’s forces are weak forces and exist in non -polar compounds and noble gases .As compared to hydrogen bonds they are weak in nature because of strong dipole -dipole interaction in hydrogen bonding.
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?
What are electrophiles and nucleophiles? Explain with examples.
Differentiate between the principle of estimation of nitrogen in an organic compound by
(i) Dumas method and
(ii) Kjeldahl's method.
Identify the reagents shown in bold in the following equations as nucleophiles or electrophiles:
(a) CH3COOH + HO- → CH3COO- + H2O
(b) CH3COCH3 + C-N → (CH3)2 C (CN) (OH)
(c) C6H5 + CH3C+O → C6H5COCH3
If the photon of the wavelength 150 pm strikes an atom and one of its inner bound electrons is ejected out with a velocity of 1.5 × 107 ms–1, calculate the energy with which it is bound to the nucleus.
Energy of an electron in the ground state of the hydrogen atom is –2.18 × 10–18 J. Calculate the ionization enthalpy of atomic hydrogen in terms of J mol–1.
The velocity associated with a proton moving in a potential difference of 1000 V is 4.37 × 105 ms–1. If the hockey ball of mass 0.1 kg is moving with this velocity, calculate the wavelength associated with this velocity.
What causes the temporary and permanent hardness of water?
Identify the functional groups in the following compounds
Describe the change in hybridisation (if any) of the Al atom in the following reaction.
For the following equilibrium, Kc = 6.3 × 1014 at 1000 K
NO (g) + O3 (g) ↔ NO2 (g) + O2 (g)
Both the forward and reverse reactions in the equilibrium are elementary bimolecular reactions. What is Kc, for the reverse reaction?
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