Lakhmir Singh & Manjit Kaur Test: Acids, Bases & Salts - Class 9 MCQ

Calcium hydroxide reacts with carbon dioxide to form calcium carbonate.

Aqueous calcium hydroxide reacts with carbon dioxide to form a white precipitate, calcium carbonate, and water.

Ca(OH)₂(s) + CO₂(g) → CaCO₃(s) + H₂O(g)

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 of about 14 while sodium carbonate is a weak base so it can have pH 9.

The chemical name for microcosmic salt is sodium ammonium phosphate and hence the chemical formula is Na(NH₄)HPO₄ . Also, when this salt is heated till it is red, it leaves a transparent glass of sodium phosphate.

Natural indicators are obtained from natural sources. All of the above examples are natural indicators. A solution of china rose turns green in a basic solution and bright pink or magenta in an acidic solution. Morning glories contain an anthocyanin called "heavenly blue anthocyanin" which changes from purplish red at pH 6.6 to blue at pH 7.7. Blueberries change from blue (around pH 2.8 — 3.2) to red in a strongly acidic solution.

Current is the rate of flow of charge. NaCl an ionic solid. An ionic solid consists of a lattice of Na+ and Cl ions in which these ions are fixed in their places. Solid NaCI does not contain any mobile charge carriers that can facilitate the flow of charge. But molten NaCI contains free mobile ions Na+ and Cl- ions which allow the passage of current.

It is an example of a double displacement reaction in which an acid (carbon dioxide) reacts with base (calcium hydroxide) to form salt and water.

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

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

Ferrous sulphate →FeSO₄⋅7H₂O

Copper sulphate →CuSO₄⋅5H₂O

Magnesium sulphate →MgSO₄⋅7H₂O

Sodium chloride →NaCl

Sodium chloride imparts a yellow colour to the Bunsen flame. This can be interpreted due to the emission of excess energy absorbed as radiation in the visible region.

When an alkali or alkaline earth metal (or its salt) is introduced in the flame, the valence electrons of the metal absorb energy and are excited to the higher energy level. When excited electrons return to their ground state, they release the absorbed energy as visible light.

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 of about 14, while sodium carbonate is a weak base to have pH 9.

Sodium carbonate is known as soda ash or washing soda Na₂CO₃ • IOH₂O. It is the sodium salt of carbonic acid. It is white hygroscopic in nature and has an alkaline taste. It is used as a water softener.

Calcium hydroxide reacts with carbon dioxide to form calcium carbonate.

Aqueous calcium hydroxide reacts with carbon dioxide to form a white precipitate, calcium carbonate, and water.

Ca(OH)₂(s) + CO₂(g) → CaCO₃(s) + H₂O(g)

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.

Current is the rate of flow of charge. NaCl an ionic solid. An ionic solid consists of a lattice of Na+ and Cl ions in which these ions are fixed in their places. Solid NaCI does not contain any mobile charge carriers that can facilitate the flow of charge. But molten NaCI contains free mobile ions Na+ and Cl- ions which allow the passage of current.

All carbonates react with acids to produce salt, water and carbon dioxide gas. H2SO4 + CuCO₃ —> CuSO₄ + H₂O + CO₂

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

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

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

Magnesium sulfate is an inorganic salt containing magnesium, sulphur and oxygen. It is often encountered as the heptahydrate sulfate mineral epsomite commonly called Epsom salt taking its name from bitter saline spring in Epsom in Surrey.