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The pKa of a weak acid (HA) is 4.5. The pOH of an aqueous buffered solution of HA in which 50% of the acid is ionized is
4.5
2.5
9.5
7.0
C.
9.5
For buffer solution
as HA is 50% ionized so [Salt] = [Acid]
pH = 4.5 pH + pOH = 14
⇒ pOH = 14 – 4.5 = 9.5
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Assuming that water vapour is an ideal gas, the internal energy change(∆U) when 1 mol of water is vapourised at 1 bar pressure and 100°C, (Given: Molar enthalpy of vapourisation of water at 1 bar and 373 K = 41 kJ mol-1 and R = 8.3 J mol–1K–1 will be) –
4.100 kJ mol–1
3.7904 kJ mol–1
37.904 kJ mol–1
41.00 kJ mol–1
C.
37.904 kJ mol–1
∆ng =1−0 =1
∆H =∆U +∆ngRT
∆U =∆H −∆ngRT
= 41 – 8.3 × 10-3 × 373
= 37.9 kJ mol-1
Which of the following sets of quantum numbers represents the highest energy of an atom?
n = 3, l = 1, m = 1, s = +½
n = 3, l = 2, m = 1, s = +½
n = 4, l = 0, m = 0, s = +½
n = 3, l = 0, m = 0, s = +½
B.
n = 3, l = 2, m = 1, s = +½
Which of the following hydrogen bonds is the strongest?
O – H …… N
F – H …… F
O – H ….. O
O – H …… F
B.
F – H …… F
The hydrogen bond in HF is strongest, because fluorine is the most electronegative element.
In the reaction,
2Al(s) + 6HCl(aq) → 2Al3+ (aq) + 6Cl¯(aq) + 3H2(g)
6L HCl(aq) is consumed for every 3L H2(g) produced
33.6 L H2(g) is produced regardless of temperature and pressure for every mole Al that reacts
67.2 L H2(g) at STP is produced for every mole Al that reacts
11.2 L H2(g) at STP is produced for every mole HCl (aq) consumed
D.
11.2 L H2(g) at STP is produced for every mole HCl (aq) consumed
2Al(s) + 6HCl(aq) → 2Al3+ (aq) + 6Cl¯(aq) + 3H2(g)
For each mole of HCl reacted, 0.5 mole of H2 gas is formed at STP.
1 mole of an ideal gas occupies 22.4 lit at STP.
Volume of H2 gas formed at STP per mole of HCl reacted is 22.4 × 0.5 litre
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