Chemistry

91. Which one of the following gases produces a red light when electricity

Which one of the following gases produces a red light when electricity flows through it ?

[amp_mcq option1=”Helium” option2=”Argon” option3=”Nitrogen” option4=”Neon” correct=”option4″]

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Neon gas produces a red light when electricity flows through it.
When an electric current passes through a low-pressure gas in a tube, the gas atoms are excited and emit light as they return to their ground state. Different gases emit light of characteristic wavelengths (colors). Neon gas specifically emits a bright reddish-orange light when used in discharge tubes, famously known as “neon signs.”
Helium typically emits a white, yellowish, or pinkish-orange light. Argon typically emits blue or violet light. Nitrogen can emit pink, orange, or yellow light depending on conditions. Other colors in commercial “neon signs” are often achieved by using different noble gases (like argon for blue) or by coating the inside of the tube with phosphors that fluoresce different colors when excited by the ultraviolet light emitted by gases like mercury vapor or argon.

92. Which one of the following statements about alkaline earth metals is N

Which one of the following statements about alkaline earth metals is NOT true ?

[amp_mcq option1=”Strontium salts burn with a red flame” option2=”Barium metal is used in medicine to examine the alimentary canal of a patient by X-ray” option3=”Green plants need magnesium in order to make the chlorophyll that trap the energy from sunlight in photosynthesis” option4=”Red colour of gemstone Ruby is due to the element beryllium present in it” correct=”option2″]

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The statement “Barium metal is used in medicine to examine the alimentary canal of a patient by X-ray” is NOT true.
For X-ray examination of the alimentary canal (Barium meal), a suspension of Barium *sulfate* (BaSO4) is used as a contrast medium. Barium sulfate is very insoluble and thus passes through the digestive system safely. Barium *metal* is highly reactive and toxic, and would react with water or acids in the body, making it unsuitable and dangerous for internal consumption or medical use in this manner.
A) Strontium salts (e.g., SrCl2) do burn with a red flame, used in fireworks. C) Magnesium is a crucial component of chlorophyll, essential for photosynthesis in green plants. D) The red colour of ruby is due to the presence of chromium ions (Cr3+) substituted into the aluminum oxide (Al2O3) lattice; beryllium is a component of other gemstones like emerald (which is beryl, a beryllium aluminum silicate, colored by chromium or vanadium). Statements A, C, and D are all factual statements (or factually correct denials, in the case of D’s claim about beryllium). Statement B is factually incorrect regarding the *form* of Barium used in medicine.

93. Which one of the following ingredients does NOT constitute paint ?

Which one of the following ingredients does NOT constitute paint ?

[amp_mcq option1=”Turpentine oil (thinner)” option2=”Poly-hydroxy phenols (anti-skinning agent)” option3=”Thiourea (accelerator)” option4=”Titanium dioxide (pigment)” correct=”option3″]

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Thiourea is NOT a standard ingredient that constitutes paint.
Typical paint formulations include Pigments (like Titanium dioxide for white color), Binders (resins or polymers that form a film), Solvents or Thinners (like turpentine oil or water to adjust viscosity), and various Additives (such as driers, anti-skinning agents like poly-hydroxy phenols, dispersants, etc.). Thiourea is an organic compound with various uses, including in resins, fertilizers, and as a vulcanization accelerator in rubber, but it is not a common or standard component of paint.
Turpentine oil is a common solvent/thinner. Poly-hydroxy phenols are used as anti-skinning agents. Titanium dioxide is a widely used white pigment. These are all standard ingredients or types of ingredients found in paints.

94. Magnesium is used in

Magnesium is used in

[amp_mcq option1=”fireworks to make a bright white light” option2=”gemstones in jewellery” option3=”examination of alimentary canal of the patient” option4=”purification of water” correct=”option1″]

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Magnesium is used in fireworks to make a bright white light.
Magnesium metal burns rapidly in air with a brilliant white flame, producing magnesium oxide (MgO). This property makes it useful in fireworks, flares, and incendiary devices to create intense light.
B) Gemstones in jewellery are typically minerals like corundum (ruby, sapphire), diamond, beryl, etc., which do not primarily contain magnesium as a main component providing aesthetic value in this context. C) Examination of the alimentary canal often uses Barium sulfate (BaSO4) as a contrast medium in X-rays, not magnesium. D) While magnesium compounds can be involved in water treatment (e.g., precipitating impurities), magnesium metal itself is not typically used directly for purification of water.

95. The principle involved in paper chromatography is

The principle involved in paper chromatography is

[amp_mcq option1=”Absorption” option2=”Partition” option3=”Solubility” option4=”Volatility” correct=”option2″]

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Paper chromatography is a separation technique based on the principle of partition. The components of a mixture distribute themselves between two phases: a stationary phase (the water molecules adsorbed on the cellulose fibers of the paper) and a mobile phase (a solvent that moves up the paper). Separation occurs because different components have different solubilities in the mobile phase and different affinities for the stationary phase, leading to differential rates of movement up the paper.
The core principle of paper chromatography is the partition of solutes between the stationary phase (water on paper) and the mobile phase (solvent). While solubility in the mobile phase and interaction with the stationary phase are factors, the overall process is governed by the partition coefficient of each substance between the two phases.
Other chromatographic techniques exist, such as thin-layer chromatography (TLC), column chromatography, and gas chromatography, which utilize principles like adsorption, partition, size exclusion, or ion exchange for separation. Paper chromatography is a specific type of partition chromatography.

96. If the formula of the sodium salt of an anion X is Na₂X, then the form

If the formula of the sodium salt of an anion X is Na₂X, then the formula of its aluminium salt would be

[amp_mcq option1=”AlX” option2=”AlX₂” option3=”Al₂X₃” option4=”AlX₃” correct=”option3″]

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The correct answer is C, Al₂X₃.
The formula Na₂X indicates that the anion X has a charge of -2 (X²⁻) because sodium (Na) has a charge of +1, and there are two sodium ions balancing the charge of one X anion (2 * +1 + charge of X = 0, so charge of X = -2). Aluminium (Al) forms ions with a charge of +3 (Al³⁺).
To form a neutral compound between Al³⁺ and X²⁻, the total positive charge must equal the total negative charge. The least common multiple of the absolute charges (3 and 2) is 6. We need two Al³⁺ ions to get a total positive charge of +6 (2 * +3) and three X²⁻ ions to get a total negative charge of -6 (3 * -2). Therefore, the formula for the aluminium salt of anion X is Al₂X₃.

97. Which one of the following is used for water softening ?

Which one of the following is used for water softening ?

[amp_mcq option1=”Mg(HCO3)2” option2=”Na3PO4” option3=”Na6P6O18” option4=”Na2HPO4” correct=”option3″]

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The correct answer is C, Na₆P₆O₁₈.
Na₆P₆O₁₈ is Sodium Hexametaphosphate, also known commercially as Calgon. It is a complex phosphate widely used as a water softening agent because it forms soluble complexes with calcium and magnesium ions, preventing them from precipitating and causing hardness.
Hard water contains high concentrations of dissolved minerals, particularly calcium (Ca²⁺) and magnesium (Mg²⁺) ions. Water softening aims to remove or neutralize these ions. Sodium salts like sodium hexametaphosphate sequester these ions, effectively “softening” the water. Sodium phosphate (Na₃PO₄) can also be used to precipitate hard ions, but hexametaphosphate is particularly effective due to its chelating ability.

98. Quartz is extensively used as a piezo electric material. It contains

Quartz is extensively used as a piezo electric material. It contains

[amp_mcq option1=”Hg” option2=”Si” option3=”Ti” option4=”Sn” correct=”option2″]

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The correct answer is B, Si.
Quartz is a crystalline mineral composed of silicon and oxygen atoms. Its chemical formula is SiO₂ (silicon dioxide). It is extensively used as a piezoelectric material due to its ability to generate an electrical charge when subjected to mechanical stress, and vice versa.
Piezoelectricity is a property of certain materials like quartz, where mechanical energy can be converted into electrical energy and vice versa. This property makes quartz useful in oscillators, sensors, and other electronic components.

99. The Soda-acid fire extinguisher contains

The Soda-acid fire extinguisher contains

[amp_mcq option1=”sulphuric acid and solution of sodium hydrogencarbonate” option2=”nitric acid and solution of sodium hydrogencarbonate” option3=”sulphuric acid and solution of sodium carbonate” option4=”sulphuric acid and solution of potassium carbonate” correct=”option1″]

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The correct option is A.
A soda-acid fire extinguisher operates based on the chemical reaction between an acid and a carbonate or bicarbonate to produce carbon dioxide gas. The standard composition of a soda-acid fire extinguisher involves sulphuric acid (H₂SO₄) and a solution of sodium hydrogencarbonate (sodium bicarbonate, NaHCO₃). When the extinguisher is activated (typically by inverting it or breaking a capsule), the acid mixes with the bicarbonate solution, leading to the reaction: H₂SO₄ + 2NaHCO₃ → Na₂SO₄ + 2H₂O + 2CO₂. The released CO₂ gas builds pressure, expelling the solution and also acts as a smothering agent to cut off oxygen supply to the fire.
Soda-acid fire extinguishers are effective against Class A fires (combustible materials like wood, paper, textiles) but are not suitable for Class B (flammable liquids), Class C (flammable gases), or Class D (metals) fires, especially not for electrical fires due to the water content. Modern fire extinguishers often use different agents like dry chemical powders, foam, or CO₂ directly.

100. Which one of the following does NOT contain COOH group ?

Which one of the following does NOT contain COOH group ?

[amp_mcq option1=”Citric acid” option2=”Lactic acid” option3=”Tartaric acid” option4=”Ascorbic acid” correct=”option4″]

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The correct option is D.
The question asks which of the listed compounds does NOT contain a carboxylic acid group (-COOH). Citric acid (C₆H₈O₇) contains three -COOH groups. Lactic acid (C₃H₆O₃) contains one -COOH group and one hydroxyl (-OH) group. Tartaric acid (C₄H₆O₆) contains two -COOH groups and two -OH groups. Ascorbic acid (C₆H₈O₆), also known as Vitamin C, is a weak acid, but its acidity primarily arises from enol groups, not carboxylic acid groups. Its structure is based on a lactone ring and does not contain a -COOH functional group.
Citric acid is found in citrus fruits. Lactic acid is produced in muscles during strenuous exercise and found in sour milk. Tartaric acid is found in grapes and tamarinds. Ascorbic acid is a vital nutrient found in fruits and vegetables, essential for various metabolic processes.
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