Chemistry Challenge Quiz

The relative atomic mass of Bromine which consists of two isotopes; ⁷⁹Br and ⁸¹Br is 79.9. Calculate the relative abundance of ⁷⁹Br in the mixture.

• 40%

• 45%

• 55%

• 80%

A solution contains 35.0 % (w/w) HBr and has the density of 1.30 gmL^-1. Calculate the molarity of this solution. [Relative Atomic Mass: Br = 79.9; H = 1]

• 6.00 M

• 5.00 M

• 5.62 M

• 5.80 M

Aluminium, Al reacts with sulphuric acid, H₂SO₄ according to the following equation.

2Al + 3H₂SO₄ → Al₂(SO₄)₃ + 3H₂.

If 1.00 g Al is placed in a solution containing 50.0 cm³ 0.1 M H₂SO₄ calculate the number of moles of H₂ will be formed. [Relative Atomic Mass: Al = 27.0; H = 1.0; O = 16.0; S = 32.1]

• 0.060 mol

• 0.005 mol

• 0.010 mol

• 0.100 mol

A piece of iron wire weighing 1.63 g is converted to Fe²⁺ (aq) and requires 21.9 mL of KMnO₄ solution for its titration. Calculate the molarity of the KMnO₄ solution. Given below the reaction occurred during the titration.

[Relative Atomic Mass: H = 1.0; Fe = 55.9; Mn =54.9; O = 16.0]

5Fe²⁺(aq) + MnO₄^-(aq) + 8H⁺(aq) → 5Fe³⁺ (aq) + Mn²⁺(aq) + 4H₂O(l)

• 1.33 M

• 2.67 x 10^-4 M

• 0.267 M

• 14.9 M

The second line of the Balmer series occurs at a wavelength of 486 nm. Calculate the energy difference between the initial and final levels of the hydrogen atom in this emission process.

[c = 3.0 x 10⁸ ms^-1; h = 6.6256 x 10^-34 Js; R_H = 2.18 x 10^-18 J / 1.097 x 107 m^-1]

• 2.44 x 10¹⁸ J

• 4.09 x 10^-19 J

• 4.09 x 10^-22 J

• 1.07 x 10^-48 J

Select the electronic configuration which is belongs to an element that forms simple ion with a charge of -2.

• 1s²2s²2p⁴

• 1s²2s²2p⁶3s²3p⁶3d¹4s²

• 1s²2s²2p⁵

• 1s²2s²2p⁶3s²3p⁶3d⁷4s²

Choose the line(s) appear in the emission spectrum of atomic hydrogen.

I. the infrared region

II. ultraviolet region

III. visible region

• I only

• I and II

• II and III

• I, II, and III

Determine the possible quantum number(s) for the valence electrons of aluminium at ground state.

[Proton Number: Al = 13]

I. n=3 , l = 0, m = 0, s = +½

II. n=3 , l = 1, m = -1, s = +½

III. n=3 , l = 2, m = -1, s = +½

• I only

• I and II

• II and III

• I, II, and III

Choose the CORRECT statement which is represent the periodicity of elements when going left to right across the period.

• Electronegativity decreases.

• Atomic size increases.

• Effective nuclear charge increases.

• The valence electrons are held weakly.

The electronic configurations of element P and element Q are as follows:

P: 1s² 2s² 2p⁶ 3s²

Q: 1s² 2s² 2p⁵

When P and Q combine to form a compound, determine the most possible formula of this compound and the type of bonding between them.

Formula = ​ ​ (a)  

Type of bonding = ​ ​ (b)  

• PQ2
• P2Q
• P2Q3
• electrovalent
• covalent
• hydrogen bond