Acid, Base and Salt

31. Which one of the following is the chemical formula of Hypobromous acid

Which one of the following is the chemical formula of Hypobromous acid ?

Subscribe on YouTube
HBrO₄
HOBr
HBr
HBrO₃
This question was previously asked in
UPSC NDA-1 – 2021
Download PDFAttempt Online
The chemical formula of Hypobromous acid is HOBr.
Hypobromous acid is a weak acid with the chemical formula HOBr or HBrO. It belongs to the group of hypohalous acids (HOX, where X is a halogen).
The other options represent different bromine oxyacids:
– HBrO₄ is perbromic acid (bromine in +7 oxidation state).
– HBr is hydrogen bromide (hydrobromic acid).
– HBrO₃ is bromic acid (bromine in +5 oxidation state).
In HOBr, bromine is in the +1 oxidation state.

Join Our Telegram Channel

32. Which one of the following will NOT produce carbon dioxide on reacting

Which one of the following will NOT produce carbon dioxide on reacting with an aqueous solution of hydrochloric acid ?

Join Our Telegram Channel
Limestone
Quick Lime
Chalk
Marble
This question was previously asked in
UPSC NDA-1 – 2019
Download PDFAttempt Online
Quick Lime will NOT produce carbon dioxide on reacting with an aqueous solution of hydrochloric acid.
Hydrochloric acid (HCl) reacts with carbonates (like in Limestone, Chalk, and Marble, which are primarily CaCO₃) to produce carbon dioxide gas, a salt, and water. The reaction is: CaCO₃(s) + 2HCl(aq) → CaCl₂(aq) + H₂O(l) + CO₂(g).
Quick Lime is calcium oxide (CaO). Calcium oxide is a basic oxide. When it reacts with water, it forms calcium hydroxide (Ca(OH)₂, slaked lime). Calcium hydroxide then reacts with hydrochloric acid in a neutralization reaction: Ca(OH)₂(aq) + 2HCl(aq) → CaCl₂(aq) + 2H₂O(l). This reaction produces calcium chloride (a salt) and water, but no carbon dioxide. Alternatively, if CaO reacts directly with HCl without forming Ca(OH)₂ first (e.g., if HCl solution is added directly to solid CaO), the reaction is CaO(s) + 2HCl(aq) → CaCl₂(aq) + H₂O(l), again producing salt and water, but no CO₂.
Substances containing carbonate or bicarbonate ions will react with acids to produce carbon dioxide. Oxides and hydroxides react with acids in neutralization reactions, typically producing salt and water.

Subscribe on YouTube

33. The equivalent weight of oxalic acid in C₂H₂O₄.2H₂O is

The equivalent weight of oxalic acid in C₂H₂O₄.2H₂O is

Subscribe on YouTube
45
63
90
126
This question was previously asked in
UPSC NDA-1 – 2019
Download PDFAttempt Online
The formula given is for hydrated oxalic acid, C₂H₂O₄.2H₂O. Oxalic acid (C₂H₂O₄ or HOOC-COOH) is a diprotic acid, meaning it can donate two protons (H⁺). The equivalent weight of an acid is its molar mass divided by the number of acidic hydrogens that participate in the reaction (also called its basicity). In typical acid-base reactions, oxalic acid dihydrate reacts as a diprotic acid, donating both protons.
– The molar mass of C₂H₂O₄ = (2 × 12.01) + (2 × 1.01) + (4 × 16.00) = 24.02 + 2.02 + 64.00 = 90.04 g/mol.
– The molar mass of 2H₂O = 2 × (2 × 1.01 + 16.00) = 2 × 18.02 = 36.04 g/mol.
– The molar mass of C₂H₂O₄.2H₂O = 90.04 + 36.04 = 126.08 g/mol.
– Oxalic acid is a diprotic acid, meaning it has 2 acidic hydrogens.
– Equivalent weight = Molar mass / number of acidic hydrogens = 126.08 g/mol / 2 = 63.04 g/equivalent.
– Among the options, 63 is the closest value.
If the question were asking for the equivalent weight of *anhydrous* oxalic acid (C₂H₂O₄) reacting as a diprotic acid, the answer would be 90/2 = 45. If it reacted as a monoprotic acid, the equivalent weight would be 90 or 126 depending on whether anhydrous or hydrated form is considered as the basis for molar mass. However, the most common standard use of oxalic acid in volumetric analysis is as the dihydrate, reacting as a diprotic acid.

Join Our Telegram Channel

34. Which one of the following is the number of water molecules that share

Which one of the following is the number of water molecules that share with two formula unit CaSO₄ in plaster of Paris ?

Join Our Telegram Channel
One
Two
Five
Ten
This question was previously asked in
UPSC NDA-1 – 2018
Download PDFAttempt Online
In plaster of Paris (CaSO₄ · ½ H₂O), one formula unit of CaSO₄ is associated with half a molecule of water. Therefore, two formula units of CaSO₄ share one molecule of water (2 * ½ H₂O = 1 H₂O).
Plaster of Paris is calcium sulfate hemihydrate (CaSO₄ · ½ H₂O). This chemical formula indicates the ratio of calcium sulfate to water molecules in the crystal structure.
When plaster of Paris is mixed with water, it rehydrates to form gypsum (CaSO₄ · 2H₂O), a hard solid. This process is exothermic and is the basis for its use in casting and construction.

Subscribe on YouTube

35. Which one of the following is NOT true for bleaching powder ?

Which one of the following is NOT true for bleaching powder ?

Join Our Telegram Channel
It is used as a reducing agent in chemical industries
It is used for bleaching wood pulp in paper factories
It is used for disinfecting drinking water
It is used for bleaching linen in textile industry
This question was previously asked in
UPSC NDA-1 – 2018
Download PDFAttempt Online
The correct answer is A) It is used as a reducing agent in chemical industries.
Bleaching powder, chemically Calcium Oxychloride (CaOCl₂), is a strong oxidizing agent due to the presence of available chlorine. It acts by releasing nascent oxygen or chlorine, which oxidizes coloured substances or kills microbes.
A) Reducing agents cause reduction and are themselves oxidized. Bleaching powder’s action is primarily oxidation, not reduction. Therefore, it is used as an *oxidizing* agent, not a reducing agent. This statement is NOT true.
B), C), and D) are correct uses of bleaching powder. It is widely used as a bleaching agent for materials like wood pulp and textiles (linen) and as a disinfectant for water supplies and surfaces.
The bleaching and disinfecting properties of bleaching powder are due to its decomposition in the presence of carbon dioxide or acids, releasing hypochlorous acid (HOCl) or chlorine gas, which are powerful oxidizing agents. CaOCl₂ + CO₂ → CaCO₃ + Cl₂ or CaOCl₂ + 2HCl → CaCl₂ + H₂O + Cl₂ or CaOCl₂ + H₂O → Ca(OH)₂ + Cl₂

Subscribe on YouTube

36. Which one of the following is the chemical formula of Washing Soda ?

Which one of the following is the chemical formula of Washing Soda ?

Subscribe on YouTube
NaHCO₃
Na₂CO₃·10H₂O
Na₂CO₃·5H₂O
NaOH
This question was previously asked in
UPSC NDA-1 – 2018
Download PDFAttempt Online
The correct answer is B) Na₂CO₃·10H₂O.
Washing soda is the common name for hydrated sodium carbonate. While anhydrous sodium carbonate is Na₂CO₃ (soda ash), the most common hydrated form used as washing soda is sodium carbonate decahydrate, with the chemical formula Na₂CO₃·10H₂O. This compound contains ten molecules of water of crystallization per molecule of sodium carbonate.
Sodium carbonate is used in various applications, including as a water softener (hence “washing soda”), in glass manufacturing, in the production of detergents and other chemicals. Sodium bicarbonate (NaHCO₃) is baking soda, which is different and used as a leavening agent and antacid. Sodium hydroxide (NaOH) is caustic soda, a strong base used in soap making and other industrial processes.

Join Our Telegram Channel

37. Brine is an aqueous solution of

Brine is an aqueous solution of

Subscribe on YouTube
NaCl
NaOH
NaHCO₃
Na₂CO₃
This question was previously asked in
UPSC NDA-1 – 2018
Download PDFAttempt Online
The correct answer is A) NaCl.
Brine is an aqueous solution of sodium chloride (NaCl), commonly known as table salt. It is a solution of salt dissolved in water, typically with a high concentration of NaCl. Seawater is a naturally occurring brine, although brine can also be produced by dissolving rock salt deposits in water.
Brine is used for various purposes, including food preservation (pickling), industrial processes (like chlor-alkali production), road de-icing, and as a heat transfer fluid. The concentration of NaCl in brine can vary widely, but it is generally significantly higher than that of normal drinking water.

Join Our Telegram Channel

38. Which one of the following gives the highest amount of hydrogen ions (

Which one of the following gives the highest amount of hydrogen ions (H⁺) ?

Subscribe on YouTube
Sodium hydroxide solution
Milk of magnesia
Lemon juice
Gastric juice
This question was previously asked in
UPSC NDA-1 – 2018
Download PDFAttempt Online
The correct answer is D) Gastric juice.
The amount of hydrogen ions (H⁺) in a solution determines its acidity, measured by pH. A lower pH indicates a higher concentration of H⁺ ions and thus higher acidity.
A) Sodium hydroxide solution (NaOH) is a strong base, having a very high pH and thus a very low concentration of H⁺ ions.
B) Milk of magnesia (Mg(OH)₂) is a weak base, having a high pH but lower than NaOH, still a very low concentration of H⁺ ions compared to acids.
C) Lemon juice contains citric acid and has a pH typically between 2.0 and 2.5, indicating a significant concentration of H⁺ ions.
D) Gastric juice in the stomach contains hydrochloric acid (HCl) and has a very low pH, typically ranging from 1.5 to 3.5. This extremely low pH indicates a very high concentration of H⁺ ions, necessary for digesting proteins and killing ingested microorganisms. Comparing the typical pH values, gastric juice is the most acidic among the options, meaning it has the highest concentration of hydrogen ions.
pH is defined as the negative logarithm (base 10) of the hydrogen ion concentration: pH = -log₁₀[H⁺]. Therefore, a decrease of 1 unit in pH corresponds to a tenfold increase in H⁺ concentration. Gastric juice’s low pH (e.g., 2) means a much higher H⁺ concentration than lemon juice (e.g., 2.5).

Join Our Telegram Channel

39. Which of the following properties is true for a tooth paste ?

Which of the following properties is true for a tooth paste ?

Subscribe on YouTube
It is acidic
It is neutral
It is basic
It is made up of Calcium phosphate, the material of tooth enamel
This question was previously asked in
UPSC NDA-1 – 2018
Download PDFAttempt Online
The correct answer is C) It is basic.
Toothpaste is typically alkaline (basic) with a pH generally ranging from 7.5 to 10. The basic nature of toothpaste helps to neutralize the acids produced by bacteria in the mouth after eating. These bacterial acids are responsible for eroding tooth enamel and causing cavities. By creating a more alkaline environment, toothpaste helps protect teeth from decay.
Tooth enamel is primarily composed of calcium phosphate in the form of hydroxyapatite. While toothpaste often contains ingredients like calcium carbonate, dicalcium phosphate, or fluoride compounds to help clean, strengthen enamel, or aid remineralization, toothpaste itself is not *made up* of enamel. Its primary function related to pH is to counteract acidity.

Join Our Telegram Channel

40. The chemical name of baking soda is

The chemical name of baking soda is

Join Our Telegram Channel
Na₂CO₃
NaHCO₃
CaCO₃
NaOH
This question was previously asked in
UPSC NDA-1 – 2017
Download PDFAttempt Online
The correct chemical formula for baking soda is NaHCO₃.
Baking soda is the common name for sodium bicarbonate. Its chemical formula is NaHCO₃.
Option A, Na₂CO₃, is sodium carbonate (washing soda). Option C, CaCO₃, is calcium carbonate (limestone). Option D, NaOH, is sodium hydroxide (caustic soda). Understanding common chemical names and formulas is essential.

Subscribe on YouTube
Page 1Page 2Page 3Page 4Page 5