Solubility products of Al(OH)3 and Zn(OH)2 are 8.5 × 10-23 and 1.8 × 10-4 respectively. If both Al3+ and Zn2+ ions are present in a solution, which one will be precipitated first on addition of NH4OH?
Al(OH)3
Zn(OH)2
Both (a) and (b)
None of these
In a reversible isothermal process, the change in internal energy is
zero
positive
negative
None of these
Based on the following thermochemical equations
H2O (g) + C(s) → CO (g) + H2 (g); H = 131 kJ
CO (g) + O2(g) → CO2 (g); H = -282 kJ
H2 (g) + O2 (g) → H2O (g); H =-242 kJ
C (s) + O2 (g) → CO2 (g); H = X kJ
the value of X will be
-393 kJ
-655 kJ
+393 kJ
+655 kJ
The first ionisation potential of Na, Mg, Al and Si are in the order
Na < Mg > Al < Si
Na > Mg > Al > Si
Na < Mg < Al > Si
Na > Mg > Al < Si
A.
Na < Mg > Al < Si
On moving along a period, since the electron is added to the same shell, the nucleus holds the outer shell more tightly, thus size decreases. Hence, to remove an electron from outer shell, large amount of energy is required. Thus, along a period, ionisation potential increases. Al (element of III A group) however, have lower IP as compared to Mg. This is because, in case of Mg, the electron is removed from the completely filled 3s orbital. Hence, required a large amount of energy. Thus, the order of first IP of given elements is
Na < Mg > Al < Si
Elements of which group form anions most readily?
Oxygen group
Nitrogen group
Halogens
Alkali metals