Metals are good conductor of electricity because they contain free electrons .

Si and Ge are used for making transistors .

1 amu = 1.66 x 10^-24 g

E = mc²

c = velocity of light (3 x 10¹⁰ cm/s)

= 1.66 X 10^-24 g X (3 x 10¹⁰ cm/s)²

= 1.49 x 10^-3 ergs

Binding energy = mass defect x E

= 1.2 x 10^-4 erg/nucleus

Note : It is per nucleus and not per nucleon

A compound could be optically active only when it contains at least one asymmetric carbon atom or chiral centre .

CCl₃COOH is the strongest acid because (-I) nductive effect increases with increase in number of chlorine atoms and therefore , acidic strength also increases .

Hydrofluoric acid shows the intermolecular hydrogen bonding due to the small size of fluorine and high electronegativity of fluorine .

Note :  Hydrofluoric acid is found in polymeric compound [(HF)_n] and liquid state due to then H-bonding .

Crystalline form of silica is called quartz .

In the third row's elements , the value of ionisation potential increases from left to right with breaks , where the atoms have some what stable configuration .

An acid is a substance which has a tendency to donate H⁺ ion and gives conjugated base .(Bronsted concept)

$\underset{\mathrm{acid}}{({\mathrm{CH}}_3{)}_2\stackrel{+}{{\mathrm{NH}}_2}}-{\mathrm{H}}^{+}$ $\to$ $\underset{\mathrm{conjugate} \mathrm{base}}{({\mathrm{CH}}_3{)}_2\mathrm{NH}}$

CH₃COONa $\rightleftharpoons$ CH₃COO^- + Na⁺

pH of buffer = pK_a + log $\frac{\left[{\mathrm{CH}}_3{\mathrm{COO}}^{-}\right]}{\left[{\mathrm{CH}}_3\mathrm{COOH}\right]}$

= 4·74 + log $\frac{500 \times 0.2}{500 \times 0.1}$

= 5.04

pH of a buffer does not change with dilution .