Materials Used in the Preparation of Substances like Soap, Glass, Ink, Paper, Cement, Paints, Safety Matches and Gun-Powder
Materials Used in the Preparation of Substances like Soap, Glass, Ink, Paper, Cement, Paints, Safety Matches and Gun-Powder MCQ Questions
13.
Flint glass, used for making optical lenses and prisms because of its high refractive index, contains:
Approach
The question asks about the composition of flint glass, specifically the key ingredient responsible for its high refractive index, making it suitable for optical lenses and prisms. This requires knowledge of common glass compositions and their properties.
Step-by-step
- Understand Flint Glass: Flint glass is a type of optical glass known for its high refractive index and relatively high dispersion. These properties are crucial for applications like lenses and prisms.
- Identify Key Components of Glass: Glass is primarily composed of silica (\(\text{SiO}_2\)), along with various modifying oxides that alter its properties.
- Recall Flint Glass Composition: Historically, flint glass was made using calcined flint (a form of silica). Modern flint glass, however, incorporates heavy metal oxides to achieve its characteristic optical properties. The most common and effective heavy metal oxide used for this purpose is lead oxide.
- Role of Lead Oxide: Lead oxide (\(\text{PbO}\)) significantly increases the refractive index and dispersion of glass. The higher the lead content, the higher the refractive index. This makes it ideal for optical components where light bending (refraction) is a primary requirement.
Correct Option:
A) Lead oxide — Flint glass is characterized by the inclusion of lead oxide (\(\text{PbO}\)) in its composition. Lead oxide is responsible for giving flint glass its high refractive index and high dispersion, properties that are essential for optical lenses and prisms.
Incorrect Options
- B) Cerium oxide — Cerium oxide (\(\text{CeO}_2\)) is primarily used as a polishing agent for glass and in some specialized glasses for its UV absorption properties, not typically as a primary component for high refractive index in common optical flint glass.
- C) Boric oxide — Boric oxide (\(\text{B}_2\text{O}_3\)) is a key component of borosilicate glass (e.g., Pyrex), which is known for its low thermal expansion and chemical resistance, not primarily for a high refractive index in the context of flint glass.
- D) Magnesium oxide — Magnesium oxide (\(\text{MgO}\)) is used in some glass compositions to increase hardness and durability, but it does not contribute to a high refractive index in the way lead oxide does for flint glass.
14.
Crooke's glass, which is used to make lenses that cut off ultraviolet radiation, contains:
Approach
The question asks about the specific component used in Crooke's glass to block ultraviolet (UV) radiation. This is a factual question related to the composition of specialized glass types.
Step-by-step
- Crooke's glass is a type of glass specifically designed to absorb or block ultraviolet radiation.
- This property is achieved by incorporating certain metallic oxides into the glass composition during manufacturing.
- Among the given options, cerium oxide is known for its strong absorption of UV radiation.
- When added to glass, cerium oxide acts as a UV filter, making the glass suitable for applications like lenses that protect against UV light.
Correct Option:
C) Cerium oxide is the key ingredient in Crooke's glass that provides its UV-blocking properties. It effectively absorbs ultraviolet radiation, preventing it from passing through the glass.
Incorrect Options
- A) Antimony trisulphide: This compound is not primarily used in glass for UV absorption. It has various applications, but not as a UV filter in lenses.
- B) Boric oxide: Boric oxide (B2O3) is a common component in borosilicate glass, which is known for its thermal resistance, but it does not specifically impart strong UV-blocking capabilities in the way cerium oxide does for Crooke's glass.
- D) Lead oxide: Lead oxide is used in lead glass (crystal glass) to increase its refractive index and density, giving it brilliance. However, it is not used to cut off ultraviolet radiation; in fact, some lead glasses can transmit UV light.
15.
Coloured glass is generally obtained by fusing ordinary glass with small amounts of:
Approach
The question asks about the common method for producing coloured glass. Coloured glass is created by adding specific substances to the molten glass mixture during its manufacturing process. We need to identify which type of additive is primarily responsible for imparting colour.
Step-by-step
- Ordinary glass is primarily composed of silica (\(\text{SiO}_2\)), soda (\(\text{Na}_2\text{CO}_3\)), and lime (\(\text{CaCO}_3\)).
- To introduce colour, specific chemical compounds are added to this molten glass mixture. These compounds absorb certain wavelengths of light and transmit or reflect others, giving the glass its characteristic colour.
- Metal oxides are well-known for their ability to impart vibrant colours to glass. For example, cobalt oxide gives blue, chromium oxide gives green, iron oxides can give green or brown, and gold chloride can give ruby red.
- These metal oxides are fused with the ordinary glass at high temperatures, becoming an integral part of the glass structure.
Correct Option:
C) Metal oxides are commonly used to produce coloured glass. They are added in small amounts to the molten glass mixture, and their ions absorb specific wavelengths of light, resulting in the desired colour.
Incorrect Options
- A) Organic dyes only: Organic dyes are generally not suitable for colouring glass because they tend to decompose at the high temperatures required for glass manufacturing. While some specialized organic pigments might be used for surface coatings, they are not typically fused within the glass itself to create coloured glass.
- B) Sulphuric acid: Sulphuric acid (\(\text{H}_2\text{SO}_4\)) is a strong acid and is primarily used in etching glass or in certain chemical processes, but it does not impart colour to glass when fused with it.
- D) Sodium chloride: Sodium chloride (\(\text{NaCl}\)), or common salt, is a component used in some glass formulations (e.g., to lower melting points or improve workability), but it does not directly act as a colouring agent. While sodium can influence the colour in some specific complex glass compositions (e.g., in combination with other elements), it is not the primary substance for general coloured glass production.
16.
The addition of cobalt oxide to molten glass imparts which colour to the glass?
Approach
This question tests knowledge about the use of metal oxides as coloring agents in glass manufacturing. Different metal oxides impart distinct colors to glass by absorbing specific wavelengths of light.
Step-by-step
- Glass is typically colorless, but various impurities or additives can give it color.
- Transition metal oxides are commonly used as coloring agents because their d-orbitals can absorb certain wavelengths of visible light, allowing the complementary color to be transmitted.
- Cobalt oxide (\(\text{CoO}\) or \(\text{Co}_2\text{O}_3\)) is a well-known coloring agent in glass and ceramics.
- When cobalt oxide is added to molten glass, it dissolves and the cobalt ions (typically \(\text{Co}^{2+}\)) interact with the glass matrix.
- These cobalt ions absorb light in the red and yellow regions of the spectrum, causing the glass to appear blue. This is a characteristic property of cobalt in glass.
Correct Option:
D) Blue — Cobalt oxide is widely used to produce a distinctive deep blue color in glass, often seen in stained glass, art glass, and some types of bottles.
Incorrect Options
- A) Yellow — Yellow color in glass is typically imparted by compounds like cadmium sulfide, titanium oxide, or iron in an oxidizing atmosphere.
- B) Green — Green color in glass is usually achieved by adding iron oxides (especially \(\text{Fe}_2\text{O}_3\) in a reducing atmosphere or chromium oxide (\(\text{Cr}_2\text{O}_3\)).
- C) Red — Red color in glass can be produced by adding copper (in a reducing atmosphere), selenium, or gold (ruby glass).
17.
Quartz glass, valued for its high melting point and transparency to ultraviolet light, is made from:
A.
Silica and boric oxide
ANSWER :
D. Pure silica alone
Approach
The question asks about the composition of quartz glass, highlighting its key properties like high melting point and transparency to UV light. Understanding the basic chemistry of different types of glass is crucial here.
Step-by-step
- Identify the core material: Quartz glass is essentially a form of glass made from quartz. Quartz itself is a crystalline form of silicon dioxide (\(\text{SiO}_2\)).
- Consider the properties: The properties mentioned (high melting point, UV transparency) are characteristic of pure silica glass. Impurities or other additives generally lower the melting point and can affect transparency, especially to UV light.
- Evaluate the options:
- Options A, B, and C involve adding other oxides (boric oxide, lead oxide, soda ash) to silica. These additions are typically made to lower the melting point of silica, make it easier to work with, or impart other specific properties (e.g., lead glass for high refractive index). However, these additions would generally compromise the high melting point and UV transparency characteristic of pure quartz glass.
- Option D, "Pure silica alone," directly corresponds to the definition and properties of quartz glass. Quartz glass is synonymous with fused silica, which is made by melting naturally occurring quartz crystals or synthetic silica.
- Conclude: The unique properties of quartz glass are due to its composition of nearly pure silicon dioxide.
Correct Option:
D) Pure silica alone. Quartz glass, also known as fused quartz or fused silica, is made by melting high-purity silica (silicon dioxide, \(\text{SiO}_2\)). Its excellent transparency to ultraviolet light and high melting point are direct consequences of its pure silica composition and the strong covalent bonds within the silica network.
Incorrect Options
- A) Silica and boric oxide: This combination forms borosilicate glass (e.g., Pyrex), which has a lower coefficient of thermal expansion than ordinary glass, making it resistant to thermal shock. However, the addition of boric oxide lowers its melting point compared to pure silica and alters its UV transmission properties.
- B) Silica and lead oxide: This mixture forms lead glass (or crystal glass). Lead oxide significantly increases the refractive index and density of the glass, giving it brilliance, but it lowers the melting point and does not offer the same UV transparency as pure silica.
- C) Silica and soda ash: This combination, along with lime (calcium oxide), forms soda-lime glass, which is the most common type of glass used for windows and bottles. Soda ash (\(\text{Na}_2\text{CO}_3\)) acts as a flux, drastically lowering the melting point of silica, making it much easier to work with. However, soda-lime glass has a much lower melting point and poor UV transparency compared to quartz glass.
18.
Ordinary blue-black writing ink is essentially a solution of:
A.
Antimony trisulphide in glue
B.
Tannic acid, gallic acid and ferrous sulphate along with a dye
C.
Titanium dioxide in linseed oil
D.
Calcium carbonate in water
ANSWER :
B. Tannic acid, gallic acid and ferrous sulphate along with a dye
Approach
The question asks about the primary composition of ordinary blue-black writing ink. This requires knowledge of the historical and chemical composition of traditional inks.
Step-by-step
- Traditional blue-black writing inks, often referred to as iron gall inks, have been used for centuries.
- Their characteristic color and permanence are derived from a chemical reaction involving specific organic acids and an iron salt.
- The key components are tannic acid (or gallic acid, derived from gallnuts), ferrous sulphate (an iron salt), and a dye (often blue) to provide initial color before the iron-gall complex fully develops and darkens.
- When these components mix, ferrous tannate/gallate is formed, which is soluble and light-colored. Upon exposure to air, it oxidizes to form insoluble ferric tannate/gallate, which is dark blue-black and permanent.
- A dye is added to make the ink visible immediately upon writing, as the full dark color develops over time due to oxidation.
Correct Option:
B) Tannic acid, gallic acid and ferrous sulphate along with a dye. This combination correctly describes the main ingredients of traditional blue-black iron gall ink. Tannic acid and gallic acid react with ferrous sulphate to form a complex that oxidizes to a permanent blue-black color, while a dye provides initial visibility.
Incorrect Options
- A) Antimony trisulphide in glue — Antimony trisulphide is used in fireworks, matches, and some pigments, but not as a primary component of ordinary writing ink. Glue might be used as a binder in some applications, but not with antimony trisulphide for writing ink.
- C) Titanium dioxide in linseed oil — Titanium dioxide is a white pigment used in paints, coatings, and sunscreens. Linseed oil is a drying oil used as a binder in oil paints and varnishes. This combination would produce a white paint, not blue-black writing ink.
- D) Calcium carbonate in water — Calcium carbonate is a white solid found in chalk, limestone, and marble. While it can be suspended in water to make a white liquid, it is not a component of blue-black writing ink. It is often used as a filler or antacid.
