Chemistry

301. For manufacturing of glass, which among the following is used as a sou

For manufacturing of glass, which among the following is used as a source of silica ?

[amp_mcq option1=”Fine clay soil” option2=”Wood powder” option3=”Coconut shell” option4=”Sand” correct=”option4″]

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Glass is primarily composed of silica (silicon dioxide, SiO₂). The main raw material used as a source of silica for glass manufacturing is sand, specifically high-purity silica sand (often called quartz sand). Other components like soda ash (sodium carbonate) and limestone (calcium carbonate) are added to lower the melting point and improve workability.
– Glass is mainly made of silica (SiO₂).
– The primary natural source of silica used in glass manufacturing is sand.
– High purity silica sand is preferred for glassmaking.
Fine clay soil contains silica, but it also contains many impurities (like alumina, iron oxides) that would affect the clarity and properties of the glass. Wood powder and coconut shells are organic materials and not sources of silica for glassmaking.

302. Which among the following is the popular method for manufacture of amm

Which among the following is the popular method for manufacture of ammonia ?

[amp_mcq option1=”Ostwald’s process” option2=”Haber-Bosch process” option3=”Electric furnace process” option4=”Electrolysis process” correct=”option2″]

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The industrial manufacture of ammonia (NH₃) from nitrogen (N₂) and hydrogen (H₂) is achieved through the Haber-Bosch process. This process involves reacting nitrogen from the air with hydrogen, usually derived from natural gas, at high temperature (400-450°C) and high pressure (150-250 atm) over an iron catalyst.
– Ammonia (NH₃) is synthesized from N₂ and H₂.
– The industrial method is called the Haber-Bosch process.
– It uses high temperature, high pressure, and an iron catalyst.
Ostwald’s process is used for the industrial production of nitric acid (HNO₃) from ammonia. Electrolysis is a process used to decompose substances using electricity. Electric furnaces are used for melting metals and other high-temperature processes, but not specifically for the Haber-Bosch synthesis.

303. Which among the following statements is not correct with respect to al

Which among the following statements is not correct with respect to allotropes of Carbon ?

[amp_mcq option1=”Graphite is a good conductor of electricity.” option2=”Diamond is the hardest substance known.” option3=”Fullerene is one of the allotropes of carbon.” option4=”Next to diamond, graphite is the second hardest known substance.” correct=”option4″]

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Diamond is indeed the hardest naturally occurring substance known. Graphite, another allotrope of carbon, has a layered structure that allows the layers to slide over each other. This makes graphite very soft, greasy to touch, and suitable for use as a lubricant and in pencil leads. It is far from being the second hardest known substance; many materials, both natural and synthetic, are significantly harder than graphite.
– Allotropes are different structural modifications of an element.
– Diamond is the hardest known substance.
– Graphite is soft and used as a lubricant.
– Fullerene is an allotrope of carbon.
– Graphite’s soft nature contradicts the statement that it is the second hardest substance.
Other allotropes of carbon include carbon nanotubes, graphene, and amorphous carbon. The different properties of carbon allotropes arise from the different ways carbon atoms are bonded together in their structures.

304. Which one of the following is the correct arrangement of metals in the

Which one of the following is the correct arrangement of metals in the decreasing order of their reactivity ?

[amp_mcq option1=”Iron, Sodium, Silver, Copper” option2=”Silver, Copper, Iron, Sodium” option3=”Sodium, Copper, Silver, Iron” option4=”Sodium, Iron, Copper, Silver” correct=”option4″]

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The reactivity of metals decreases as you move down the reactivity series. The reactivity series ranks metals based on their tendency to lose electrons and undergo oxidation. A metal higher in the series can displace a metal lower in the series from its salt solution. The standard reactivity series places Sodium (Na) very high, followed by Iron (Fe), then Copper (Cu), and finally Silver (Ag) is quite low. Therefore, the decreasing order of reactivity is Sodium, Iron, Copper, Silver.
– Metals are ranked by their reactivity (tendency to lose electrons).
– The reactivity series is K > Na > Ca > Mg > Al > Zn > Fe > Pb > H > Cu > Hg > Ag > Au > Pt.
– The metals in the options are Sodium (Na), Iron (Fe), Copper (Cu), Silver (Ag).
– Their order in the series is Na > Fe > Cu > Ag.
Highly reactive metals like Sodium react vigorously with cold water. Moderately reactive metals like Iron react with steam. Less reactive metals like Copper and Silver do not react with water or steam and are found uncombined in nature more often.

305. What is the specific purpose of using potassium hydroxide during the s

What is the specific purpose of using potassium hydroxide during the saponification process ?

[amp_mcq option1=”To obtain soaps which are hard on the skin” option2=”To obtain soaps which are soft on the skin” option3=”To obtain natural fragrance” option4=”To make the saponification very economical” correct=”option2″]

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Saponification is the process of hydrolyzing fats or oils using an alkali (strong base) to produce soap and glycerol. The type of alkali used influences the properties of the resulting soap. Sodium hydroxide (NaOH) typically yields hard soaps, suitable for bar soap. Potassium hydroxide (KOH) typically yields soft or liquid soaps, often used in liquid hand soap, shaving cream, or soft paste soaps. Therefore, potassium hydroxide is used to obtain soaps which are soft on the skin or in liquid form.
– Saponification uses a strong base to hydrolyze fats/oils.
– NaOH produces hard soaps.
– KOH produces soft or liquid soaps.
– The softness of the soap is desirable for certain applications like liquid soaps or those used on the skin.
Natural fragrances are added separately to the soap formulation and are not a result of using KOH specifically. While the cost of NaOH vs KOH can be a factor in manufacturing, the primary reason for choosing KOH is to achieve a softer soap consistency.

306. Toothpaste prevents tooth decay by :

Toothpaste prevents tooth decay by :

[amp_mcq option1=”neutralizing the excess acidity.” option2=”means of emulsification.” option3=”the action of fluoride.” option4=”making a coat of calcium over the teeth surface.” correct=”option3″]

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The correct answer is C) the action of fluoride.
The primary mechanism by which toothpaste prevents tooth decay is through the action of fluoride. Fluoride incorporated into toothpaste strengthens tooth enamel by promoting the formation of fluorapatite, a crystalline structure more resistant to acid dissolution than hydroxyapatite, the main component of enamel.
Fluoride also aids in the remineralization of early enamel lesions and inhibits the ability of plaque bacteria to produce acids. While toothpaste may also contain ingredients that help neutralize acids (Option A), fluoride is the key active ingredient specifically responsible for the significant reduction in dental caries incidence seen with the widespread use of fluoride toothpaste. Option B (emulsification) is unrelated to preventing decay. Option D (making a coat of calcium) is an inaccurate description of how toothpaste ingredients work.

307. Among the following, which is not the correct method for keeping the

Among the following, which is not the correct method for keeping the curd ?

[amp_mcq option1=”Keeping in stainless steel vessel” option2=”Keeping in copper vessel” option3=”Keeping in plastic vessel” option4=”Keeping in glass vessel” correct=”option2″]

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The correct answer is B) Keeping in copper vessel.
Curd is acidic due to the presence of lactic acid produced during fermentation. Acidic substances can react with certain metals, such as copper, to form potentially harmful salts.
Keeping acidic food like curd in copper vessels is not recommended because the acid can react with the copper metal. This reaction can leach copper ions into the food, potentially leading to health issues if consumed regularly in significant amounts. Stainless steel, plastic, and glass are non-reactive materials commonly used for storing acidic food items safely.

308. An iron nail dipped in copper sulphate solution turns brown. This is d

An iron nail dipped in copper sulphate solution turns brown. This is due to which one of the following types of reactions ?

[amp_mcq option1=”Addition reaction” option2=”Decomposition reaction” option3=”Substitution reaction” option4=”Displacement reaction” correct=”option4″]

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The correct answer is D) Displacement reaction.
This reaction involves a more reactive metal (iron, Fe) displacing a less reactive metal (copper, Cu) from its salt solution (copper sulphate, CuSO4). The general form of a displacement reaction involving metals is A + BX → AX + B, where A is more reactive than B.
The reaction is represented as: Fe(s) + CuSO4(aq) → FeSO4(aq) + Cu(s). The iron nail gets coated with brown copper metal. This is a classic example illustrating the reactivity series of metals, where iron is higher than copper. It is also a redox reaction where iron is oxidized and copper ions are reduced. While substitution reactions also involve replacement, “displacement reaction” is the specific term used for this type of reaction involving elements and compounds.

309. Which one of the following apparatus is used for separating benzene an

Which one of the following apparatus is used for separating benzene and water mixture ?

[amp_mcq option1=”Round bottom flask” option2=”Conical flask” option3=”Separating funnel” option4=”Dean and Stark apparatus” correct=”option3″]

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The correct answer is C) Separating funnel.
A separating funnel is a piece of laboratory glassware used to separate immiscible liquids, i.e., liquids that do not mix and form distinct layers, based on their densities. Benzene and water are immiscible; benzene is less dense than water.
When a mixture of benzene and water is placed in a separating funnel, the two liquids separate into layers (water at the bottom, benzene at the top). The stopper is then opened, and the lower layer (water) is drained out through the stopcock until the interface between the two layers reaches the stopcock. The stopcock is then closed, and the upper layer (benzene) is collected in a separate container. Round bottom flasks and conical flasks are used for mixing, heating, or storage, not for separating immiscible liquids. A Dean and Stark apparatus is used for determining moisture content by distillation.

310. Which of the hydrocarbons are arranged as per the increasing order of

Which of the hydrocarbons are arranged as per the increasing order of their boiling points ?

[amp_mcq option1=”Methane, Butane, Propane, Heptane” option2=”Propane, Butane, Pentane, Octane” option3=”Propane, Butane, Heptane, Methane” option4=”Octane, Ethane, Methane, Propane” correct=”option2″]

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The correct answer is B) Propane, Butane, Pentane, Octane.
For a homologous series of hydrocarbons like alkanes, the boiling point generally increases with increasing molecular weight, which corresponds to an increasing number of carbon atoms. This is because larger molecules have stronger van der Waals forces (London dispersion forces), requiring more energy (higher temperature) to overcome them and transition from liquid to gas phase.
The number of carbon atoms in the given hydrocarbons are: Methane (C1), Ethane (C2), Propane (C3), Butane (C4), Pentane (C5), Heptane (C7), Octane (C8). Arranging them by increasing carbon number gives the expected order of increasing boiling points: C1 < C2 < C3 < C4 < C5 < C6 < C7 < C8. Option B lists hydrocarbons in the order: Propane (C3), Butane (C4), Pentane (C5), Octane (C8), which corresponds to increasing carbon numbers (3 < 4 < 5 < 8), and thus increasing boiling points.
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