Question Library

pH = - log [0.25] = - log[ \(\frac{25}{100}\) ] = - (log 25 - log 100) = - ( 1.397 - 2) = - ( - 0.60) pH = 0.60 N.B : You can use your mathematical table, to check for log 25, if you don't have log on your calculator. Already with our knowledge of lorithm, log 100 = 2. Thus we were asked to find pOH not pH. However, there is relationship between the two as: pH + pOH = 14 0.60 + pOH = 14 pOH = 14 - 0.60 pOH = 13.40

We want the number of charges on both sides of the equation to be the same. i.e. number of charges on the reactant side = the number of charges on the product side. -1 + 8 = 2 7 = 2 difference in number of charges = 5, hence Y = 5.

Argon is an inert gas that's non-flammable, non-toxic, and has low reactivity with metals.Argon produces a stable, quiet, and smooth arc. It's also versatile and can be used on a variety of metals, including mild steel, stainless steel, and aluminum. As a result, it is the most common noble gas used for electric arc welding.

Water is a solvent, and soft water is more aggressive at leaching metals from pipes. Soft water has little or no minerals, so it pulls minerals from the pipes it travels through. Thus, Soft water can dissolve lead from pipes because it's more reactive and lacks minerals.

Ligands are molecules or ions that bond to a central metal atom or ion. Water molecules can act as ligands when bonded to transition metals. When a water molecule acts as a ligand, it's called an aqua ligand.

DDT is not found naturally in the environment as it is a synthetic chemical compound that was created for use as an insecticide. On the other hand, NO (nitric oxide), CO (carbon monoxide), and HCHO (formaldehyde) can all be found in nature to some extent, either as byproducts of natural processes or produced by living organisms.DDT (Dichlorodiphenyltrichloroethane) is an air pollutant that is not found in nature

In order to calculate this, it suffices to calculate the solubility of Ag, so as to know the amount lost. \(K_{sp} = [Ag^{+}][Cl^{-}]\) Let the solubilty of Ag and Cl = d \(2 \times 10^{-10} = d \times d= d^{2}\) \(d = \sqrt{2\times10^{-10}}\) = \(1.414 \times 10^{-5}moldm^{-3}\)

1 mol → 96500 x 2 0.5 mol → X X = 0.5 x 96500 x 2 = 9.650 x 10\(^4\)C

Faraday’s First Law of Electrolysis states that the mass of a substance deposited at any electrode is directly proportional to the amount of charge passed. Mathematically it can be expressed as follows – m ∝ Q Removing the proportionality sign m=ZQ. Therefore, option D is the correct answer

Heat absorbed by water = (mC\Deltat) = (50 x 4.2 x 14.3) = 3003.0J = 3.003kJ no of moles of ethanol = \(\frac{mass}{molar mass}\) = \(\frac{0.46}{46}\) = 0.01 mol. Therefore, heat of combustion of ethanol = \(\frac{heat absorbed by water}{no of mole of ethanol}\) = \(\frac{-3.003}{0.01}\) = - 300.3kj/mol

A powdered substance typically reacts faster than the granular or solid form of the same substance because of its larger surface area. This is because more particles are exposed to the other reactant, which increases the likelihood of collisions and the rate of reaction.

In a chemical system in equilibrium, an increase in temperature for an endothermic reaction (\DeltaH = + 180.6 kJmol-1) will cause the equilibrium position to shift to the right, thereby favouring an increase in the yield of the product i.e NO. On the other hand, a decrease in temperature will cause the equilibrium position to shift to the left, favouring an increase in the yield of the reactants on the LHS. The reverse is the case when it is an exothermic reaction (\DeltaH = -ve). The correct answer is option B

Solid species are not shown in equilibrium constant expressions because their concentrations do not change significantly during a reaction. The activity of pure liquids and solids is 1 and the activity of a solution can be estimated using its concentration. So, pure liquids and solids actually are involved, but since their activities are equal to 1, they don't change the equilibrium constant and so are often left out. The equilibrium constant expression only contains those species whose concentrations could change significantly during the reaction - gaseous and dissolved species. Option D is the correct answer.

Allotropy is the existence of two or more different physical forms of an element. For instance, Carbon exhibit allotropy as it exists in about three different forms, physically such as Diamond, Graphite and amorphous Carbon.

Vulcanization is a process that involves heating rubber with sulphur to improve its strength and elasticity. The process is carried out by mixing latex with sulphur and heating it. Other vulcanizing agents, like selenium and tellurium, are sometimes used, but sulphur is the most common.