NTSE Test: Acids, Bases & Salts - Class 9 MCQ

NaCl is a neutral salt formed by the reaction between strong acid HCl and strong base NaOH. The reaction occurs as follows.

Ferrous sulphate →FeSO₄⋅7H₂O

Copper sulphate →CuSO₄⋅5H₂O

Magnesium sulphate →MgSO₄⋅7H₂O

Sodium chloride →NaCl

An insoluble milky white precipitate of calcium carbonate and water is produced when calcium hydroxide reacts with carbon dioxide gas. The reaction follows a double displacement reaction.

Groups IIA, IIIA, and IVA metals are less reactive than the neighbouring alkali metals. Thus Al and Zn are less reactive metals than Na, K and Mg.

When an acid reacts with a metal, a metal salt and hydrogen are formed. However, this depends if the metal is reactive or not. For example, magnesium, (Mg) is a violently reactive metal to hydrochloric acid) Therefore, making magnesium chloride and hydrogen

Metal oxides react with acid to form salt and water because most of the metal oxides are basic or amphoteric in nature.

Sodium aluminate and hydrogen gas are formed when sodium hydroxide reacts with aluminium metal.
2NaOH + 2Al + 2H₂O ⇨ 2NaAlO₂ + 2H₂

When acids react with carbonates, such as calcium carbonate (found in chalk, limestone and marble), salt, water and carbon dioxide are made. In general: Acid + Metal carbonate Salt + Water + Carbon dioxide

A salt associated with the water of crystallization is known as a hydrate.

Decay of teeth is because of the sweetening agents we eat as it increases the acidity inside the mouth, which can be prevented if the toothpaste used is alkaline or basic in nature. Baking soda or sodium hydrogen carbonate is also used to clean the teeth as it is alkaline in nature.

Non-metals do not react with acids. Thus, option b is correct.

 pH above 7 confirms the compound to be alkaline in nature so it can be either sodium carbonate or sodium hydroxide as HCl and CH₃COOH are acidic in nature. Sodium hydroxide is a strong base, so it has the highest pH about 14 while sodium carbonate is a weak base so it can have pH 9.

Seawater contains MgCl₂ brine, so salt made from seawater contains this as an impurity, sea salt:

The chemical formula for the plaster of Paris is
and is better known as calcium sulfate hemihydrate.

We should know that borax, also known as sodium borate, sodium tetraborate, or disodium tetraborate. We should know that borax is the main component of detergents, cosmetics, and enamel glazes. We also use it as a fire retardant and anti-fungal compound in the manufacture of fiberglass, as a flux in metallurgy. We should know that borax is composed of sodium, borax, oxygen and water.
We should know that borax can be found as anhydrous, pentahydrate or dehydrated salt. We should note that the anhydrous and decahydrate forms are the most common forms of borax. The borax decahydrate chemical formula is Na2B4O7.10H2O
Na₂B₄O7.10H₂O
. So, from this we can say that option A is correct.