Chemistry MCQs

Notes:
Methanol (CH₃OH) is also known as Wood Alcohol. It’s a solvent in many chemical processes and is a component of automobile antifreeze.

Notes:
Natural rubber becomes soft at high temperature (>335 K) and brittle at low temperatures (<283 k) and shows high water absorption capacity. It is soluble in non-polar solvents and is non-resistant to attack by oxidising agents. To improve upon these physical properties, a process of vulcanisation is carried out. This process consists of heating a mixture of raw rubber with sulphur and an appropriate additive at a temperature range between 373 K to 415 K. On vulcanisation, sulphur forms cross links at the reactive sites of double bonds and thus the rubber gets stiffened.
 In the manufacture of tyre rubber, 5% of sulphur is used as a crosslinking agent

Notes:
Helium, a noble gas, is the second most abundant element in the universe after Hydrogen. It is colorless, odorless, tasteless, non-toxic, and non-reactive because its outermost electron shell is full with two electrons. This complete outer shell gives it the stability that defines the Noble Gases. Despite its abundance in the universe, Helium is relatively rare on Earth, primarily obtained from natural gas wells.

Notes:
One important character of Ionic solids is that they readily get dissolved in water

Notes:
If water is heated ,it vapor pressure will increase. Latent heat is the reason for high temperature and pressure of vapour.

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Increasing the amount of iron in steel generally leads to increased hardening. This is due to the formation of a solid solution where carbon atoms occupy interstitial spaces in the iron lattice, enhancing strength and hardness. Steel’s carbon content is crucial. higher carbon levels (up to 2.1%) improve hardness but reduce ductility. The melting point of steel is also influenced by its composition, but the primary effect of increasing iron is hardening.

Notes:
Zinc oxide (ZnO) can undergo a chemical reaction depending on the pH of the solution. In acidic conditions, it can react to form zinc ions (Zn²⁺), while in alkaline conditions, it can form zincates. This behavior is due to its amphoteric nature, which allows it to react with both acids and bases. In contrast, calcium oxide (CaO) is basic, ferric oxide (Fe₂O₃) is generally inert in neutral pH, and ferrous oxide (FeO) is less reactive in varying pH levels.

Notes:
Sublimation is the process where a solid turns directly into a gas without passing through the liquid phase.

• Iodine: Sublimes at about 113.7°C, releasing purple vapors.
• Naphthalene: Sublimes at around 80°C, commonly used in mothballs.
• Camphor: Sublimes at approximately 175°C, used in medicinal and aromatic applications.

All three substances can undergo sublimation upon heating, making the correct answer “All of them.”

Notes:
In India, the Double Sulphitation is the most commonly used method for refining of sugar. Also, it is the cheapest process of refining sugar as compared to other available process.

Notes:
The compounds of carbon having double or triple bonds between the carbon atoms are known as unsaturated carbon compounds.