Mixing acid with base gives salt, water and heat. Carbon dioxide is not produced when acid and bases are mixed.

• Plaster of Paris is a mixture of powdered and heat-treated gypsum.
• It does not generally shrink or crack when dry, making it an excellent medium for casting moulds.
• It is also known as Calcium sulphate hemihydrate.
  Hence option B is the right answer.

Plaster of Paris is a product of calcium. If pure gypsum (CaSo4. 2H2O) is heated from 1000 to 1900 C, three quarters of the burn is removed, and the resulting substance is called Paris plaster (CaSO4. ½H2O). Chemically plaster of Paris semisolid calcium sulfate. is.

• Sodium hydroxide (NaOH), also known as lye and caustic soda, is an inorganic compound. It is a white solid and highly caustic metallic base and alkali salt which is available in pellets, flakes, granules, and as prepared solutions at a number of different concentrations.
• Sodium hydroxide forms an approximately 50% (by weight) saturated solution with water. Sodium hydroxide is soluble in water, ethanol and methanol.
• This alkali is deliquescent and readily absorbs moisture and carbon dioxide in air.

Chemical name of washing soda is Sodium carbonate. It is synthesized through Solvay’s process. It is also known as soda ash and soda crystals. The formula for washing soda is Na₂CO₃.10H₂O. It is use to remove the hardness of water and for washing clothes.

Zinc salts in the form of ZnO used in deodorants act as anti-bacteria as well as antiperspirants. ZnO has anti-microbial properties and used to absorb the odour.

HSO₄^- can accept a proton to form sulphuric acid (acid) as well as donate proton in the form of H⁺ to form SO₄²⁻. Thus, it can act as both Bronsted acid as well as a base

HCl only gives H⁺ thus is an acid.
O²⁺​neither gives nor acceptsH+ion.
Na_2​CO₃​can accept H⁺ thus is a base. 

Magnesium hydroxide is the inorganic compound with the chemical formula Mg(OH)₂. It occurs in nature as the mineral brucite. It is a white solid with low solubility in water. Magnesium hydroxide is a common component of antacids, such as milk of magnesia, as well as laxatives.

The blue litmus will turn red or pink under an acidic condition. And turns purple or remains blue in basic or alkaline conditions

Common salt solution is neutral in nature i.e., pH near about 7.

Hydronium ion is the common name for the aqueous cation H₃O⁺. This ion is produced by the protonation of water. When an Arrhenius acid is dissolved in water, the Arrhenius acid molecules in solution give up a proton resulting in a positive ion.

It does not exist in a free state and is extremely reactive. It is very acidic.

A Lewis base is a chemical species that has its outermost orbital filled with an electron lone pair not involved in any bonding and it can donate that lone pair in the solution. Ammonia is a Lewis base as it has a lone pair and it can donate it to form ammonium ion.

Similarly, a Lewis acid is a chemical species with an empty orbital that can accept an electron lone pair.

Both Lewis acid and base accept/donate lone pair to form a Lewis adduct with each other.

• Acids are sour in taste and change the colour of blue litmus to red. An acid is a substance which provides hydrogen ion (H⁺) on dissolving in water.

• Acids are proton donors and tend to accept a lone pair of electrons. The number of removable hydrogen ions from an acid is called basicity of that acid. Some examples are HCL, H₂SO_4, HNO_3.

• Ammonia gas turns red litmus paper blue. It has a characteristic sharp, choking smell. It also makes damp red litmus paper turn blue.
• Ammonia forms a white smoke of ammonium chloride when hydrogen chloride gas, from concentrated hydrochloric acid, is held near it.
• Litmus Paper Definition: Filter paper which has been treated with a natural water-soluble dye obtained from lichens. The resulting piece of paper, called 'litmus paper', can be used as a pH indicator.

• The chemical formula of Hydronium ion is H₃O+.

• Its concentration relative to hydroxide is a direct measure of the pH of a solution.

• It can be formed when an acid is present in water or by the combination of a H+ ion with an H₂O molecule.

• It has a trigonal pyramidal geometry and is composed of three hydrogen atoms and one oxygen atom.

• There is a lone pair of electrons on the oxygen giving it this shape.

• Bases are bitter and change the colour of the red litmus to blue. A base is a substance whose aqueous solution gives hydroxide ion (OH^-).

• Bases accept a proton from another substance and are the donors of a lone pair of electron. Oxides and hydroxides of metals are strong bases. The water-soluble bases are called alkalies.