Acids,Bases And Salts - Practice Test, Class 10 Science - Class 10 MCQ

When treated with dilute acid, Marble (calcium carbonate), Limestone (calcium carbonate), and Baking soda (sodium bicarbonate) all react to produce carbon dioxide gas. In contrast:

• Lime, being calcium oxide, does not release CO₂ in this reaction.

Thus, the correct answer is D.

• Mineral acids are strong acids derived from inorganic compounds.
• Hydrochloric acid, sulphuric acid, and nitric acid are all classified as mineral acids.
• Citric acid, however, is an organic acid found in citrus fruits.
• This makes citric acid the only non-mineral acid in the list.
• Thus, the correct answer is citric acid (option 2).

When equal volumes and concentrations of HCl (acid) and NaOH (base) are mixed, they react to form a neutral solution of NaCl.

The reaction can be summarised as follows:

• HCl + NaOH → NaCl + H₂O

The resulting solution has a pH of 7, which corresponds to:

• A neutral solution
• A yellowish-green colour on pH paper

Acids are characterised by their sour taste, unlike bases, which are bitter. Additionally, acids have specific effects on litmus paper:

• Acids cause blue litmus paper to turn red.
• Red litmus paper remains red in acidic solutions.

In a dilute aqueous solution, hydrochloric acid (HCl) completely dissociates into H₃O⁺ and Cl^- ions due to its strong acidic nature. The presence of H₃O⁺ is a result of the protonation of water molecules by H⁺ ions from HCl.

Therefore, the correct answer is option A, which includes both H₃O⁺ and Cl^-.

Salts are generally formed from the neutralisation reaction between acids and bases. This reaction results in ionic compounds composed of:

• Cations (with the exception of ammonium)
• Anions

While most salts are ionic, some exceptions exist where salts may have covalent characteristics. However, the general rule holds that salts are typically ionic compounds.

When a metal carbonate reacts with a dilute acid, the products are a salt, water, and carbon dioxide gas. The reaction can be represented as:

MCO₃ + H₂SO₄ → MSO₄ + H₂O + CO₂↑.

Therefore, the correct answer is CO₂ (option A).

Acetic acid (CH₃COOH) is a weak acid because it does not completely dissociate in water. This is in contrast to strong acids, which do fully dissociate. Examples of strong acids include:

• Hydrochloric acid (HCl)
• Nitric acid (HNO₃)
• Sulphuric acid (H₂SO₄)

The primary organic acid present in tomatoes is citric acid.

When certain active metals, such as aluminium or zinc, react with strong bases (like NaOH), they can produce dihydrogen gas (H₂) along with the corresponding salt and water.

For example, the reaction of aluminium with sodium hydroxide produces:

• sodium aluminate
• water
• hydrogen gas

This demonstrates that dihydrogen is a common product in such reactions.

pH is defined as the negative logarithm (base 10) of the concentration of hydrogen ions ([H⁺]) in a solution. Mathematically, it is expressed as:

pH = -log[H⁺]

This scale provides a convenient way to express the acidity or basicity of a solution:

• A lower pH value indicates a higher concentration of hydrogen ions, making the solution more acidic.
• A higher pH value indicates a lower concentration of hydrogen ions, making the solution more basic.

Litmus solution is a natural indicator.it is obtained from nature. Litmus is made up of purple dye obtained from lichen.
a) neutral solution= purple
b) acidic solution= blue to red
c) basic solution= red to blue

A universal indicator is a mixture of several different pH indicators. Each indicator changes colour at specific pH ranges, allowing the solution to display a spectrum of colours corresponding to different levels of acidity or basicity.

This makes option B correct because it accurately describes the composition of a universal indicator. The other options are incorrect:

• Option A: Refers to a mixture of a strong acid (HCl) and a strong base (NaOH), which is unrelated to indicators.
• Option C: Mentions phenolphthalein, which is just one indicator.
• Option D: Also mentions phenolphthalein, which does not function as a universal indicator on its own.

To determine the pH of a 0.00001 M (1e-5 M) HCl solution, we start by recognising that HCl is a strong acid and dissociates completely in water. This means the concentration of hydrogen ions [H⁺] from HCl is equal to the concentration of the acid, so:

• [H⁺] = 0.00001 M = 1e-5 M

The pH can be calculated using the formula:

• pH = -log[H⁺]

Substituting the [H⁺] value:

• pH = -log(1e-5) = 5

Although water autoionisation contributes a negligible amount of H⁺ (approximately 1e-7 M), at this concentration, it does not significantly affect the pH calculation. Thus, the pH remains approximately 5.

Therefore, the correct answer is C.

The question incorrectly refers to the nature of zinc metal itself, whereas its reactions with acids and bases pertain to its oxide, which is amphoteric. Therefore, none of the provided options accurately describe zinc metal's nature in this context.

Explanation:

• Property 1: It turns blue litmus red – This is true because dilute HCl is an acid, and acids turn blue litmus paper red.
• Property 3: It reacts with zinc and a gas is evolved – This is also true. When dilute HCl reacts with zinc, it produces hydrogen gas.
• Property 4: It reacts with solid sodium carbonate to give brisk effervescence – This is true as well. When dilute HCl reacts with sodium carbonate, it produces carbon dioxide gas, which causes brisk effervescence.

Property 2: It turns red litmus blue – This is incorrect because acids do not turn red litmus paper blue; this property is characteristic of bases.

Therefore, the correct combination of properties is 1, 3, and 4.

Sodium bicarbonate (NaHCO₃) is a salt derived from a weak acid, carbonic acid (H₂CO₃), and a strong base, sodium hydroxide (NaOH). When sodium bicarbonate is dissolved in water, it undergoes dissociation into:

• Na⁺ ions
• HCO₃^- ions

The bicarbonate ion (HCO₃^-) then reacts with water, resulting in the formation of:

• Carbonic acid (H₂CO₃)
• This further dissociates into:
• CO₃^2- ions
• H⁺ ions

However, since the bicarbonate ion acts as a stronger base than it does as an acid, it tends to accept protons from water. This behaviour results in a solution that is slightly basic, thereby:

• Increasing the pH of the solution above 7

Consequently, the pH of the solution becomes greater than 7 after dissolving sodium bicarbonate in pure water.

Na2Co3 is a basic salt hence, it will give basic solution.

NaCl is a neutral salt hence, it will give a neutral solution.

Red litmus turns blue in a basic solution because bases are alkaline.

• Among the options, sodium hydroxide (NaOH) is a strong base.
• This strong base will cause the red litmus to turn blue.