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]

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]

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)

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]

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

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

I. the infrared region

II. ultraviolet region

III. visible region

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

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

Phosphorous and Nitrogen are elements from group 15 of the Periodic Table. P can form PCl₅, but nitrogen cannot form NCl₅. This is because

The similar chemical properties of the elements in the periodic table is best accounted by the fact that atoms of these elements have:

Choose the correct statement(s) for the formation of ionic bonds between two atoms,

I. the difference in their electronegativity must be large.

II. one of the atoms must be that of a metal while the other must be that of a non-metal.

III. each atom must achieve octet configuration.

Choose the CORRECT statement(s) which is represent the formation of a coordinate bond.

I. ammonia reacts with hydrogen chloride.

II. gaseous hydrogen chloride is dissolved in water.

III. sodium hydroxide reacts with hydrochloric acid.

Predict the molecular shape and polarity of the CS₂ molecule. [Proton Number: C = 6, S = 16]

The bond angle for methane, ammonia and water is 109.5^o, 107^o and 104.5^o respectively. Select the causes of this trend in bond angles shown.

I. Increasing repulsion between hydrogen atoms as the bond length decreases.

II. The number of lone pairs in the molecule.

III. A lone pair having a greater repulsive force than a bonding pair.

Ethanol is much more soluble in water than is ethyl ethanoate (CH₃COOCH₂CH₃). Select the statement which helps to account for this.

Choose from the following statements which is/are true for metallic bonding.

I.             The strength of the metallic bonds depends on the number of valence electrons.

II.            The solid lattice consists of cations immersed in a sea of delocalized electrons

III.           Going down group 1, metallic bonding of the elements becomes stronger.

The phenomenon in which iron needle floats on water illustrates a properties of liquids knowns as

FIGURE 1 shows the phase equilibrium of a pure substance X. Which of the following statements is TRUE?

The equilibrium constant, K_p for the reaction

2SO₃(g) ↔ 2SO₂(g) + O₂(g) is 1.8 x 10^-5 at 350^ᵒC.

What is Kc for the reaction at the same temperature?

(Given R = 0.08206 L atm mol^-1 K^-1)

In a chemical reaction used in automotive air bag safety system, N₂ (g) is produced by the decomposition of sodium azide.

2NaN₃ (s) → 2Na (s) + 3N₂(g)

Calculate the volume of N₂, measured at 25ᵒC and 0.980 atm, produced by the decomposition of 62.5 g of NaN₃.

Consider the following reaction at certain temperature :

N₂(g) + 3H₂(g) ↔ 2NH₃ (g)

The equilibrium mixture in a 4.00 L vessel contains 1.60 mol NH₃, 0.800 mol N₂, and 1.20 mol H₂. Calculate the equilibrium constant, K_C for the reaction.

Determine the system that will shift the equilibrium position to the right if the volume is decrease.

Consider the gas-phase equilibrium system represented by the following equation :

2H₂O (g) ↔ 2H₂(g) + O₂ (g) ΔH = -286 kJmol^-1

Choose the CORRECT changes (disturbance) that will decrease the equilibrium amount of H₂O.

0.30 g of a gas occupies a volume of 82 mL at a pressure of 308 kPa and temperature of 27 ^oC. What is the relative molecular mass of the gas?

[Given 1 atm = 101.325 kPa, gas constant, R = 0.08206 L atm mol^-1 K^-1]

When the following reaction achieves equilibrium at 298K,

2NO₂ (g) ↔ N₂O₄ (g)

The partial pressures of NO₂(g) and N₂O₄ (g) are 0.45 and 0.88 atm respectively. What is the value of equilibrium constant K_c for the reaction at 298K?

[Given gas constant, R = 0.08206 L atm mol^-1K^-1]

At 460^ᵒC, the value for K_c for the following reaction is 51:

H₂(g) + I₂(g) ↔ 2HI(g)

A mixture of H₂, I₂ and HI in a vessel has the following concentrations: [H₂] = 1.0 M [I₂] = 0.10 M [HI] = 3.0 M. Which one of the following statements concerning the reaction quotient, Q_c, is TRUE for the above system?

The value of the equilibrium constant for the reaction is 0.25 at 440°C :

2HI(g) ↔ H₂(g)+ I₂(g)

At the same temperature, what would the value of the equilibrium constant be for the following reaction;

H₂(g)+ I₂(g) ↔ 2HI(g)

P (g) + 3Q (g) ↔ 2R(g)

When a mixture containing 3 mol P and 5 mol Q is allowed to achieve equilibrium, the equilibrium mixture is found to contain 2 mol R. Volume of container is 1L. The K_c for the reaction is