2021 Sc & Math Club

How many total valence electrons are participating in bonding in this molecule?

• 8

• 4

• 2

• 3

Which one of the following is the maximum number of atomic orbitals having a principal quantum number of two?

• 5

• 9

• 4

• 3

An atom of element X has the same number of electrons as Fe²⁺ ion. Which of the following statement is/are true?

i. The electron configuration of element X is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁴ 4s^2.

ii. Element X is a transition element.

iii. The electron configuration of X³⁺ ion is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d³

• i only is correct

• i and ii only are correct

• ii and iii only are correct

• i, ii and iii are correct

What kind of intermolecular bond are water moleculars form?

• Hydrogen Bonding

• Dipole-Dipole

• London Dispersion

• Bohr Bonding

A solution where [H⁺] = 1 x 10^-11 is

• acidic

• basic

• neutral

• pretty neat.

In the equation below, identify the conjugate acid.

HSO₃^- + H₂PO₄^- --> H₃PO₄ + SO₃^2-

• HSO₃^-

• H₂PO₄^-

• H₃PO₄

• SO₃^2-

X and Y are elements of the third period.

X and Y are individually heated in excess chlorine. Each product is purified and then separately added to water, producing two solutions. Both solutions have a pH of less than 5. What could be X and Y

• Na and P

• Mg and Al

• Mg and Si

• Si and P

Cl_2(g) is added to cold, aqueous NaOH. In a separate experiment, Cl_2(g) is added to hot, aqueous NaOH. Which oxidation states of Cl are found in the reactants and products of the two reactions that take place?

• 0, -1, +1 and +5

• 0, -1 and +1 only

• 0, -1 and +5 only

• 0, +1 and +5 only

What is the formula of the complex ion formed when silver chloride precipitate dissolves in excess NH₃ solution?

• [Ag(OH)₂]^-(aq)

• [Ag(NH₃)₄]²⁺(aq)

• [Ag(NH₃)₂]⁺(aq)

• [Ag(NH₃)₂]⁺(s)

Two half-cell equations are given below.

X⁴⁺(aq) + 2e -----> X²⁺(aq) E^o = +0.15 V

Y⁴⁺(aq) + 2e -----> Y²⁺(aq) E^o = +1.69 V

Which statement is true about the half-cell equations?

• Y²⁺ ions are more stable than X²⁺ ions.

• X²⁺ ions are more stable than Y²⁺ ions.

• X⁴⁺ ions are a stronger oxidising agent than Y⁴⁺ ions.

• X⁴⁺ ions could oxidise Y²⁺ ions.