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 |
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)
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
= 4·74 + log
= 5.04
pH of a buffer does not change with dilution .
What is binding energy in 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
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 .
Crystalline form of silica is called :
crystalline silicon
quartz
rock
talc
B.
quartz
Crystalline form of silica is called quartz .
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 .
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 .
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 .
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 .