Elements P, Q, R, S have 6, 11, 15, 17 electrons respectively, therefore,
P will form an electrovalent bond with R
Q will form a covalent bond with S
R will form an electrovalent bond with S
Q will form an electrovalent bond with S
Correct answer is D
P 6 = 2, 4
Q 11 = 2, 8, 1
R 15 = 2, 8, 5
S 17 = 2, 8, 7
Given the above is the electronic arrangement of PQRS elements, Q will form an electrovalent bond with S. Without argument, D is the answer because electrovalency involves the transfer of electron. Already, Q is 11 with electronic configuration of 2, 8, 1, i.e. having 1 valence electron which is ready to be lost by the atom of element Q, also, S is 17, with electronic configuration of 2, 8, 7. There the 7 valence electron of S attracts that only 1 electron to attain a stable octet structure.
Which of the following metals cannot replace hydrogen from water or steam?
Sodium
Magnesium
Iron
Copper
Correct answer is D
Metals above hydrogen in the activity series can displace or replace hydrogen present in water (H\(_2\)O) example of such metals are Ca, K, Na etc. But the metals below hydrogen in the activity series cannot replace hydrogen in the activity series example of such metals are Cu, Hg.
The conductivity of an acid solution depends on the
amount of ions present and their mobilities
mobilities of the ions present
amount of ions present
temperature of the solution
Correct answer is A
The conductivity of a solution depends on the number of charge carriers (the concentrations of the ions), the mobility of the charge carriers and their charge. Theoretically, conductivity should increase in direct proportion to concentration.
Spring water
River water
Tap water
Sea water
Correct answer is C
Tap water contains less Ca\(^{2+}\) and Mg\(^{2+}\)
Aluminium does not react with either dilute or concentrated trioxonitrate (V) acid because
it is insoluble in either dilute or concentrated trioxonitrate (V) acid
it is lower than hydrogen in the electrochemical series
the reaction with trioxonitrate (V) acid has a light activation energy
an insoluble oxide is formed on its surface which renders it passive
Correct answer is D
Aluminium doesn’t react with either dilute or concentrated trioxonitrate (V) acid because an insoluble oxide is formed on its surface which renders it passive. It will depend on the concentration of the nitric acid used…. Although aluminium reacts with dilute nitric acid to produce aluminium nitrate and hydrogen gas, concentrated (>60%) nitric acid is such a powerful oxidising agent that it instantly causes a thin layer of aluminium oxide to coat the surface of the aluminium