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# NEET Chemistry Solved Question Paper 2007

#### Multiple Choice Questions

11.

Among third row elements , the IP value :

• irregularly changes from left to right across the third row

• increases from left to right across the third row

• decrease for Na to Ar

• remains constant

B.

increases from left to right across the third row

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 .

 Third row's element Na Mg Al Si P S Cl Ar IP (eV) 5.1 7.6 6.0 8.0 11.0 10.4 13.0 15.8

12.

The conjugate base of (CH3)2NH2+ is :

• (CH3)3N

• (CH3)2NH

• (CH3)2N-

• (CH3)2N+

B.

(CH3)2NH

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

$\underset{\mathrm{acid}}{\left({\mathrm{CH}}_{3}{\right)}_{2}\stackrel{+}{{\mathrm{NH}}_{2}}}-{\mathrm{H}}^{+}$ $\to$

# 13.A buffer solution contains 500 mL of 0.2 M CH3COONa and 500 ml of 0.1 M CH3COOH .1 L of water is added to this buffer , pH before and after dilution will be (pka of CH3COOH = 4.74)3.74 5.04 5.90 7.70

B.

5.04

CH3COONa $⇌$ CH3COO- + Na+

pH of buffer = pKa + log $\frac{\left[{\mathrm{CH}}_{3}{\mathrm{COO}}^{-}\right]}{\left[{\mathrm{CH}}_{3}\mathrm{COOH}\right]}$

= 4·74 + log

= 5.04

pH of a buffer does not change with dilution .

14.

What is binding energy in ${}_{5}{}^{11}\mathrm{B}$ nucleus , if mass is 0.08181 amu ?

• 1.2 x 10-4 erg/nucleus

• 8.2 x 10-4 erg/nucleus

• 10.2 x 10-4 erg/nucleus

• 1.9 x 10-4 erg/nucleus

A.

1.2 x 10-4 erg/nucleus

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

15.

The elements commonly used for making transistors are :

• Ga and In

• C and Si

• P and As

• Si and Ge

B.

C and Si

D.

Si and Ge

Si and Ge are used for making transistors .

16.

Crystalline form of silica is called :

• crystalline silicon

• quartz

• rock

• talc

B.

quartz

Crystalline form of silica is called quartz .

17.

Hydrofluoric acid shows hydrogen bonding due to :

• high electron affinity of fluorine

• high bond dissociation energy of fluorine

• high electronegativity of fluorine

• none of the above

C.

high electronegativity of fluorine

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 .

18.

Which is the strongest acid ?

• ClCH2COOH

• CH3COOH

• Cl2CHCOOH

• CCl3COOH

D.

CCl3COOH

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

19.

Metals are good conductor of electricity because they contain :

• a network structure

• ionic bonds

• very few valence electrons

• free electrons

D.

free electrons

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

20.

Which of the compound is optically active ?

• 1 - butanol

• Ethanol

• 2 - butanol

• Isopropyl alcohol

D.

Isopropyl alcohol

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