Chemistry Half-Yearly Notes

What are the primary metals found in the Earth's crust?

Metals primarily come from the Earth's crust, including native elements like copper, silver, gold, and platinum.

What is the composition percentage of oxygen in the Earth's crust?

Oxygen makes up approximately 45% of the Earth's crust.

Which metal is found in the highest percentage in the Earth's crust after oxygen?

Silicon, which constitutes about 27% of the Earth's crust.

What are the major components of the Earth's crust?

Oxygen, silicon, iron, aluminum, calcium, sodium, magnesium, and potassium.

What defines a metal ore?

Ores are rocks that contain a high amount of a particular metal compound worth mining for extraction.

List two examples of metal ores.

Bauxite (aluminum ore) and rock salt (sodium chloride).

What is the economic viability of mining based on?

It depends on the availability of ore, amount of metal that can be extracted, extraction challenges, costs, and potential selling price.

What happens to reactive metals in the Earth's crust?

Reactive metals like iron and aluminum do not occur uncombined.

What are some characteristics of scarce metals?

Scarce metals include copper, zinc, lead, tin, mercury, silver, gold, and platinum; they are generally more expensive and used quickly due to high demand.

What is one method of extracting metals from their ores?

Reduction, which involves removing oxygen from metal oxides.

What is electrolysis used for in metal extraction?

Electrolysis is used for obtaining metals, particularly aluminum, that are difficult to extract by other methods.

What does the blast furnace do in iron extraction?

It is a fundamental component that helps reduce iron(III) oxide to molten iron.

What is the main product of electrolysis of sodium chloride?

Chlorine gas, hydrogen gas, and sodium hydroxide.

What is one environmental concern associated with the chloralkali process?

The process can generate hazardous chemicals that pose environmental risks.

Explain the concept of halogens in chemistry.

Halogens are found in Group 17 of the periodic table and are known for their high reactivity.

Name the most reactive halogen.

Fluorine is the most reactive halogen.

What color and state is bromine at room temperature?

Bromine is a reddish-brown liquid at room temperature.

How do halogens typically exist in nature?

Halogens commonly exist as diatomic molecules (e.g., F₂, Cl₂, Br₂, I₂).

Describe displacement reactions involving halogens.

A more reactive halogen can displace a less reactive halogen from its compound.

What occurs when sodium reacts with chlorine gas?

They form sodium chloride (NaCl) through an ionic reaction.

What reaction occurs during the chlorination of methane?

Substitution occurs, where hydrogen is replaced by chlorine.

What is the common oxidation state of halogens in halides?

Halogens usually exhibit a -1 oxidation state in halides.

What type of compounds can halogens form with metals?

Halogens form ionic compounds known as halides with metals.

What are some economic contributions of the chloralkali industry?

It produces fundamental materials like chlorine, sodium hydroxide, and hydrogen, crucial for various chemical processes.

Name the three products formed during the electrolysis of brine.

Chlorine gas, hydrogen gas, and sodium hydroxide.

What is the purpose of a selective membrane in the membrane cell process?

To improve the efficiency of separating products during electrolysis.

How does electrolysis yield aluminum?

The electrolysis of aluminum oxide separates aluminum from oxygen.

What is the environmental concern with mercury in the chloralkali process?

Mercury poses risks and is less commonly used due to environmental hazards.

How do halogens react with hydrogen?

Halogens react with hydrogen to produce hydrogen halides, strong acids.

What is a common safety measure to take when handling halogens?

Appropriate safety measures should be observed due to their corrosive and toxic nature.

What occurs during the reduction process in metal extraction?

Oxygen is removed from metal oxides to obtain pure metals.

Explain the term 'alloys' in metallurgy.

Alloys are mixtures of metals or non-metals that enhance certain properties.

Give an example of a common alloy and its components.

Stainless steel is an alloy made of iron, nickel, and chromium.

What role does the carbon monoxide play in iron oxide reduction?

Carbon monoxide is used to reduce iron(III) oxide to iron during extraction.

What are bi-products of the chloralkali industry that can impact the environment?

Hazardous chemicals produced during the electrolysis process that need proper management.

Describe the physical states of halogens at room temperature.

Fluorine and chlorine are gases; bromine is a liquid; iodine is a solid.

What is the effect of atomic size on halogen reactivity?

Reactivity decreases down the group due to increasing atomic size and decreased electronegativity.

What is the chemical reaction for the electrolysis of lead bromide?

Electrolysis of lead bromide yields lead and bromine.

What is the role of carbon in the extraction of metals?

Carbon acts as a reducing agent in the reduction process to obtain pure metals.

Why are some metals considered scarce?

They make up less than 2% of the Earth's crust and are in high demand.

What is the significance of the chloralkali industry in chemical manufacturing?

It provides essential raw materials for various downstream chemical processes.

What happens during the addition reaction of alkenes with halogens?

Halogens add across double bonds in alkenes, creating dibromides or similar compounds.

Mention a use for sodium hydroxide produced in the chloralkali industry.

Sodium hydroxide is used in soap making, paper production, and as a cleaning agent.

What unique properties do interhalogen compounds exhibit?

Interhalogen compounds display unique reactivities and properties distinct from pure halogens.