Among the following, which is water insoluble?
Sodium fluoride
Potassium fluoride
Beryllium fluoride
Magnesium fluoride
Assertion (A) - K, Rb and Cs form superoxides.
Reason (R) - The stability of the superoxides increases from K to Cs due to decrease in lattice energy.
The correct answer is
Both (A) and (R) are true and (R) is the correct explanation of (A).
Both (A) and (R) are true but (R) is not the correct explanation of (A).
(A) is true but (R) is not true.
(A) is not true but (R) is true.
In photoelectric effect, if the energy required to overcome the attractive forces on the electron, (work functions) of Li, Na and Rb are 2.41 eV, 2.30 eV and 2.09 eV respectively, the work function of 'K could approximately be in eV.
2.52
2.20
2.35
2.01
B.
2.20
As the size of atom (element) increases, energy required to overcome the attractive force on outermost electron decreases.
Li, Na, K and Rb are the members of same group and have the following order of size
Li < Na < K < Rb
Thus, the energy in case of K is intermediate of Rb and Na, i.e.,
2.30 < K > 2.09
or the energy for K is 2.20 eV.
Na2S2O3 reacts with moist Cl2 to form Na2SO4, HCl and X. Which one of the following is X?
H2S
SO2
SO3
S
Ni anode is used in the electrolytic extraction of
Al
Mg
Na by Down's process
Na by Castner's process
Which of the following is not correct?
LiOH is a weaker base than NaOH.
Salts of Be undergo hydrolysis
Ca(HCO3)2 is soluble in water.
Hydrolysis of beryllium carbide gives acetylene.
Assertion (A) : Alkali metals are soft and have low melting and boiling points.
Reason (R) : This is because interatomic bonds are weak.
Both (A) and (R) are not true.
(A) is true but (R) is not the correct explanation of (A).
(A) is true but (R) is false.
Both (A) and (R) are true and (R) is the correct explanation of (A).
Consider the following statements-
I. Cs+ ion is more highly hydrated than other alkali metal ions.
II. Among the alkali metals, only lithium forms a stable, nitride by direct combination with nitrogen.
III. Among the alkali metals Li, Na, K, Rb the metal, Rb has the highest melting point.
IV. Among the alkali metals Li, Na, K, Rb only Li forms peroxide when heated with oxygen.
Select the correct statement is
I
II
III
IV