Chemical Reactions and Processes

Statement 3 is incorrect because hydrogen gas does not evolve on reaction with sulphuric acid. The following reaction takes place on reaction between them: NaCl (s) + H₂SO₄ (l) -------> HCl (g) + NaHSO₄ (s)

Platinum is the most unreactive metal.Thus, it does not react with H₂SO₄ under any condition.

When H₂SO₄ reacts with metal sulphide, H₂S gas evolves.

Charcoal is left behind; water and volatile material get removed.

Chemical change is any change that results in the formation of a new chemical substance. It involves making and breaking the bonds between atoms. It cannot be reversed.

Physical change is affecting the form of a chemical substance, but not its chemical composition. It can be reversed.

Chemicals, which reduce the rate of corrosion are called corrosion inhibitors. They are of two types: cathodic and anodic. Phosphate, chromate and tungstate protect anode by forming sparingly soluble products, which are adsorbed on the surface of the metal and hence check the corrosion. Cathodic protection is done by organic amines, mercaptans, thiourea and substituted urea. These chemicals retard reduction reaction, taking place at cathode.

Deacon process is a method of preparation of chlorine by oxidation of hydrochloric acid.

During the electrolysis of aqueous solution of sodium chloride hydrogen gas is produced at the cathode, while chlorine gas is obtained at anode. There are two substances that can be reduced at the cathode: Na⁺ ions and water molecules. At cathode: Na⁺ + e^-  Â® Na       E^o_red = -2.71 V 2 H₂O + 2 e^- Â®H₂ + 2 OH^-                   E^o_red = -0.83 V It is much easier to reduce water than Na⁺ ions. Hence, the only product formed at the cathode is hydrogen gas. There are two substances that can be oxidized at the anode: Cl^- ions and water molecules. At anode:  2 Cl^- Â® Cl₂ + 2 e^-                        E^o_ox = -1.36 V 2 H₂O Â® O₂ + 4 H⁺ + 4 e^-                       E^o_ox = -1.23 V Due to closeness of the standard-state potentials for these half-reactions, we might expect a mixture of Cl₂ and O₂ gas collect at the anode. However, in practice only chlorine gas is obtained at anode.

Ziegler-Natta catalyst (titanium tetrachloride in the presence of triethylaluminium) is used in the polymerisation of ethene.

This statement is false about aluminium because aluminium liberates hydrogen from acid as well as bases. So, this option is correct.

Biodiesel is made from vegetable oils and animal fats. Biodiesel can be used as a fuel for vehicles in its pure form, but it is usually used as a diesel additive to reduce levels of particulates, carbon monoxide and hydrocarbons from diesel-powered vehicles. Biodiesel is produced from oils or fats using transesterification.

Potassium chlorate is a compound containing potassium, chlorine, and oxygen, with the chemical formula KClO3. In pure form, it is a white crystalline substance. It is the most common chlorate in industrial use, and is usually present in well-stocked laboratories. It is used as an oxidizing agent to prepare oxygen as a disinfectant, in safety matches, and in explosives and fireworks. Potassium chlorate ( KCLO3 ) decomposes upon heating to yield potassium chloride and oxygen gas. Manganese dioxide ( MnO2 ) is mixed with potassium chlorate and behaves as a catalyst for this reaction . 2 KClO³ ---( Heat with MnO2 Catalyst )----> 2 KCl + 3 O^2_.

Acids give hydrogen gas along with a salt when they react with a metal. Here, a metal carbonate reacts with an acid to give carbon dioxide and water.

Magnesium and maganese are the metals,  which liberates hydrogen with dilute nitric acid.