Chemical Reactions and Equations Test - 15

A precipitation reaction refers to the formation of an insoluble salt when two solutions containing soluble salts are combined. The insoluble salt that falls out of solution is known as the precipitate, hence the reaction's name.

Therefore in these reactions, one of the products formed is in the solid state.

Hence, option (C) is correct.

A substance is said to be reduced if it gains hydrogen or loses oxygen during a reaction and A substance is said to be oxidised if it gains Oxygen or loses Hydrogen during a reaction.

A redox reaction can be defined as a chemical reaction in which electrons are transferred between two reactants participating in it. This transfer of electrons can be identified by observing the changes in the oxidation states of the reacting species.

Therefore, we can say, statement (iii) and (iv) are correct.

Hence, option (D) is correct.

Reduction reaction in simple terms means addition of Hydrogen or removal of Oxygen atom and Oxidation reaction in simple terms means addition of Oxygen or removal of Hydrogen atom.

The reactant which gets reduced (oxidises the other products) will be called as Oxidizing Agent and the reactant which gets oxidized (reduces the other products) will be called as Oxidizing Agent.

Keeping in mind the above definitions in this reaction, we can say copper oxide is being reduced and hydrogen is being oxidised.

Hence, option (D) is correct.

A decomposition reaction can be defined as a chemical reaction in which one reactant breaks down into two or more products.

Same is carried out in the case of Digestion also. Therefore, the Question statement will be as follows,

During the process of digestion, the components of food break down into simpler substances. Hence, digestion is a “Decomposition” reaction.

Hence, option (B) is correct.

Decomposition of calcium carbonate:Calcium carbonate (lime stone) decomposes into calcium oxide (quick lime) and carbon dioxide when heated. Quick lime is the major constituent of cement.

${\mathrm{CaCO}}_3\left(\mathrm{s}\right)$$\stackrel{heat}{\to }$$\mathrm{CaO}\left(\mathrm{s}\right)+{\mathrm{CO}}_2\left(\mathrm{g}\right)$

From the above reaction we can say that the compounds obtained after the decomposition of limestone will be Calcium Oxide and Carbon Dioxide.

Hence, option (B) is correct.

Sodium sulphate chemically reacts with barium chloride in the form of their aqueous solution to form a white precipitate of barium sulphate.

${\mathrm{Na}}_2{\mathrm{SO}}_4\left(\mathrm{aq}\right)$$+\underset{(\mathrm{White} \mathrm{precipitate})}{{\mathrm{BaCl}}_2\left(\mathrm{aq}\right)\to {BaSO}_4\left(\mathrm{s}\right) }$$+2\mathrm{NaCl}\left(\mathrm{aq}\right)$

This is a double displacement reaction in which sulphate ions are displaced by chloride ions and vice-versa.

The products formed are different from the reactants in chemical composition and chemical properties thus this is the case of chemical change.

Hence, option (C) is correct.

Sodium will undergo corrosion as it is a metal and the other materials will form various products upon reaction with atmospheric gases like Oxygen, Hydrogen, Water Vapors, etc.

Hence, option (D) is correct.

Combination Reaction 

A combination reaction (also known as a synthesis reaction) is a reaction where two or more elements or compounds (reactants) combine to form a single compound (product). Such reactions are represented by equations of the following form: X + Y → XY.

If we see the reactions in options (A), (B), and (C) there are 2 reactants and 1 product.

In option (D) the reaction is an example of a Displacement reaction as the Ionic Groups is changing its position.

Hence, the option (D) is correct.

A combination reaction (also known as a synthesis reaction) is a reaction where two or more elements or compounds (reactants) combine to form a single compound (product). Such reactions are represented by equations of the following form: X + Y → XY.

Amongst the options we can see that in option (C) the reactant H₂ and O₂ combine to form only one product H₂O.

Hence, option (B) is correct.

In this Endothermic Reaction the methane absorbs energy and decomposes to 1 mol carbon and 2 mol Hydrogen Gas. The process gives a sound due the release of Hydrogen Gas.

Since, Carbon is losing hydrogen and there is an increase in the oxidation number we can say that Carboni getting Oxidised.

Hence, option (C) is correct.

While balancing a chemical equation the molecular formula, types of reactants, types of products, Physical state of Reactants and Products remains constant.

Whereas, the Stoichiometric Coefficients and Oxidation Number remains same.

Hence, option (C) is correct.

Whitewash, or calcimine, kalsomine, calsomine, or lime paint is a type of paint made from slaked lime (calcium hydroxide, $\mathrm{Ca}{\left(\mathrm{OH}\right)}_2$ ).

$\mathrm{Ca}{\left(\mathrm{OH}\right)}_2$ is made by reacting $\mathrm{CaO}$ with ${\mathrm{H}}_2\mathrm{O}$.

Hence, option (C) is correct.

A single displacement reaction is a kind of oxidation-reduction chemical reaction when an ion or element moves out of a compound, i.e., one element is replaced by the other in a compound. 

In the options (a), (b) and (c) we see that there is exchange of only one ionic group.

In the option (d) we see that it is an example of Double Displacement Reaction as there is exchange of two ionic groups.

Hence, option (D) is correct.

In option (A) Corrosion does not cause damage to iron filings, ships and metal containers which is incorrect as Oxidation of the respective metal.

In option (B)  Fats and oils are oxidised in the presence of air which is called Rancidity and the statement is correct.

In option (C) Preserving food in air tight containers helps to slow down the process of oxidation to avoid Rancidity.

In option (D) The smell of oily products changes when kept unpreserved due to Oxidation.

Hence, option (A) is correct.

A decomposition reaction occurs when one reactant breaks down into two or more products. This can be represented by the general equation: AB → A + B. Examples of decomposition reactions include the breakdown of hydrogen peroxide to water and oxygen, and the breakdown of water to hydrogen and oxygen.

Amongst the given options, in the option (C) it says that Energy is neither absorbed nor released during the electrolysis of water, but in the process of Electrolysis of Water Electric Currents are passed from the solutions and Hence, there will be a transfer of energy. So, this statement will be false.

Hence, option (B) is correct.