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
7.
Transparent soaps are manufactured by:
A.
Adding excess of sodium chloride to soap
B.
Mixing soap with sand and pumice powder
C.
Dissolving soap in ethanol and then evaporating the excess solvent
D.
Boiling soap with sodium silicate
ANSWER :
C. Dissolving soap in ethanol and then evaporating the excess solvent
Approach
Transparent soaps are a specialized type of soap that allows light to pass through. Their manufacturing process involves specific steps to achieve this transparency, primarily by preventing the formation of large soap crystals and ensuring a homogeneous mixture.
Step-by-step
- Ordinary soaps are typically opaque due to the presence of tiny, dispersed soap crystals and other impurities.
- To make soap transparent, these crystals need to be dissolved or prevented from forming in a way that scatters light.
- Ethanol (alcohol) acts as a solvent that can dissolve the soap, creating a clear solution.
- When the excess ethanol is evaporated, the soap solidifies, but because it was dissolved and then solidified without forming large crystals, it retains its transparency. Glycerine is often added during this process to enhance transparency and moisturizing properties.
Correct Option:
C) Dissolving soap in ethanol and then evaporating the excess solvent. This method is the standard procedure for producing transparent soaps. The alcohol dissolves the soap, and upon evaporation, a clear, vitreous (glass-like) soap is formed.
Incorrect Options
- A) Adding excess of sodium chloride to soap. Adding excess sodium chloride (salt) to soap solution is a process called 'salting out' or 'graining out'. It causes the soap to precipitate out of the solution, separating it from glycerine and other impurities. This process is used in the manufacturing of ordinary opaque soaps, not transparent ones, as it promotes the formation of solid soap curds.
- B) Mixing soap with sand and pumice powder. Mixing soap with sand and pumice powder would create abrasive soaps, often used for heavy-duty cleaning or exfoliation. These additives would make the soap opaque and gritty, completely contrary to the goal of transparency.
- D) Boiling soap with sodium silicate. Sodium silicate is often used as a filler or builder in laundry soaps to improve cleaning efficiency and reduce costs. It does not contribute to transparency; in fact, it can make the soap more opaque and harder.
8.
Laundry (washing) soaps generally contain fillers such as:
A.
Borax and calcium carbonate only
B.
Sodium rosinate and sodium silicate
C.
Starch and glycerol only
ANSWER :
B. Sodium rosinate and sodium silicate
Approach
The question asks about common fillers found in laundry (washing) soaps. To answer this, one needs to recall the typical composition of laundry soaps, especially the role of fillers in enhancing their properties or reducing cost.
Step-by-step
- Understand the function of fillers in soap: Fillers are substances added to soap formulations to improve certain properties like lathering, stability, or to reduce manufacturing costs. They are distinct from the primary cleaning agents (surfactants).
- Recall common soap additives: Laundry soaps often contain various additives beyond the basic soap (sodium or potassium salts of fatty acids). These include builders, optical brighteners, perfumes, and fillers.
- Evaluate the given options:
- A) Borax and calcium carbonate: Borax (sodium tetraborate) is a common laundry booster and water softener, but calcium carbonate is generally avoided in laundry soaps as it can cause soap scum, especially in hard water.
- B) Sodium rosinate and sodium silicate: Sodium rosinate is derived from rosin (a natural resin) and acts as a filler, emulsifier, and lather enhancer. Sodium silicate is a common builder and filler in laundry soaps, providing alkalinity, corrosion inhibition, and preventing redeposition of dirt. These are indeed common fillers.
- C) Starch and glycerol: Starch can be used as a filler in some applications, but it's not as universally common in laundry soaps as sodium silicate or rosinate. Glycerol is a byproduct of soap making and is often left in or added to toilet soaps for its moisturizing properties, but it's not primarily a filler in laundry soaps.
- D) Titanium dioxide: Titanium dioxide is a white pigment and opacifier, sometimes used in small quantities in soaps for appearance, but it's not a primary filler in the sense of bulk addition to laundry soaps.
- Identify the best fit: Based on the common chemical compositions of laundry soaps, sodium rosinate and sodium silicate are well-known and frequently used fillers/additives.
Correct Option:
B) Sodium rosinate and sodium silicate. Sodium rosinate improves lathering and acts as a filler, while sodium silicate acts as a builder, corrosion inhibitor, and filler, enhancing the soap's overall performance and stability.
Incorrect Options
- A) Borax and calcium carbonate only — While borax is used, calcium carbonate is generally not preferred as a filler in laundry soaps due to its tendency to form insoluble precipitates (soap scum) with soap in hard water.
- C) Starch and glycerol only — Starch is less common as a primary filler in laundry soaps compared to silicates. Glycerol is a humectant and byproduct, not typically a filler in laundry soaps.
- D) Titanium dioxide — Titanium dioxide is primarily a pigment and opacifier, not a bulk filler in laundry soaps.
9.
Glass is best classified as a/an:
C.
Super-cooled (amorphous) liquid
ANSWER :
C. Super-cooled (amorphous) liquid
Approach
The question asks for the best classification of glass. We need to understand the fundamental properties of different states of matter, especially solids and liquids, and how glass fits into these categories.
Step-by-step
- Understand Crystalline Solids: Crystalline solids have a highly ordered, repeating three-dimensional arrangement of atoms, ions, or molecules. They have sharp melting points.
- Understand Liquids: Liquids have a disordered arrangement of particles that can move past each other. They flow.
- Understand Amorphous Solids: Amorphous solids lack a long-range ordered structure. They are often described as super-cooled liquids because their particles are arranged randomly, similar to a liquid, but they are rigid and do not flow easily at room temperature. They soften gradually over a range of temperatures instead of having a sharp melting point.
- Analyze Glass: Glass is known for its lack of a definite melting point; it softens over a range of temperatures. It lacks the long-range order characteristic of crystalline solids. Its atoms are arranged randomly, but it is rigid and does not flow under normal conditions. This behavior is characteristic of an amorphous solid, which is essentially a liquid that has been cooled to a solid-like state without crystallizing, hence "super-cooled liquid."
Correct Option: C) Super-cooled (amorphous) liquid
Glass is an amorphous solid, meaning it lacks the long-range ordered structure found in crystalline solids. It is often referred to as a super-cooled liquid because its molecular arrangement is similar to that of a liquid, but its viscosity is so high that it behaves like a solid. It does not have a sharp melting point but rather softens gradually over a temperature range.
Incorrect Options
- A) Crystalline solid — Glass does not have a highly ordered, repeating atomic structure, nor does it possess a sharp melting point, which are defining characteristics of crystalline solids.
- B) Colloidal sol — A colloidal sol is a type of colloid where solid particles are dispersed in a liquid medium. Glass is a bulk material, not a dispersion of particles in another medium.
- D) Ionic crystal — Ionic crystals are a type of crystalline solid formed by ionic bonds, with a regular, repeating lattice structure of ions. Glass is not typically formed by ionic bonds and lacks the crystalline structure.
10.
Ordinary soda-lime glass used for windows and bottles is manufactured mainly by fusing:
A.
Sand, cerium oxide and sodium carbonate
B.
Sand (silica), sodium carbonate and limestone
C.
Sand, lead oxide and potassium oxide
D.
Sand, boric oxide and aluminium oxide
ANSWER :
B. Sand (silica), sodium carbonate and limestone
Approach
The question asks about the main components used to manufacture ordinary soda-lime glass, which is commonly used for windows and bottles. This requires knowledge of the basic raw materials for glass production.
Step-by-step
- Identify the type of glass: The question specifies "ordinary soda-lime glass." This is the most common and cheapest type of glass.
- Recall the primary ingredient: All glass production starts with silica (sand) as the main glass-forming agent.
- Recall modifiers for soda-lime glass: To lower the melting point of silica and make it workable, a flux is added. Sodium carbonate (soda ash) is the primary flux used in soda-lime glass.
- Recall stabilizers for soda-lime glass: To improve the durability and chemical resistance of the glass, a stabilizer is added. Limestone (calcium carbonate) is the main stabilizer in soda-lime glass, providing calcium oxide.
- Combine the main components: Therefore, the key ingredients for ordinary soda-lime glass are sand (silica), sodium carbonate, and limestone.
Correct Option: B) Sand (silica), sodium carbonate and limestone
This combination represents the three primary raw materials for manufacturing soda-lime glass. Sand (silica) is the glass former, sodium carbonate acts as a flux to lower the melting point, and limestone (calcium carbonate) provides calcium oxide, which acts as a stabilizer to improve durability.
Incorrect Options
- A) Sand, cerium oxide and sodium carbonate — Cerium oxide is used in specialized glasses, often for UV absorption or as a polishing agent, not as a primary component of ordinary soda-lime glass.
- C) Sand, lead oxide and potassium oxide — Lead oxide is a key component of lead glass (crystal glass), which is known for its high refractive index and density, and is distinct from soda-lime glass. Potassium oxide can be used in some glasses but is not the primary stabilizer for ordinary soda-lime glass.
- D) Sand, boric oxide and aluminium oxide — Boric oxide is the main component of borosilicate glass (like Pyrex), known for its thermal shock resistance. Aluminium oxide can be added to improve strength and durability but is not a primary component of ordinary soda-lime glass in the same way as limestone.
11.
Borosilicate (Pyrex) glass, used for laboratory apparatus, contains boric oxide along with silica and:
C.
A small proportion of aluminium oxide and sodium oxide
D.
A large proportion of lead oxide
ANSWER :
C. A small proportion of aluminium oxide and sodium oxide
Approach
The question asks about the composition of borosilicate (Pyrex) glass, specifically what other components it contains besides boric oxide and silica. To answer this, one needs to recall the common constituents of borosilicate glass.
Step-by-step
- Identify the primary components: Borosilicate glass is primarily composed of silica (\(\text{SiO}_2\)) and boric oxide (\(\text{B}_2\text{O}_3\)). The presence of boric oxide is what gives it its characteristic low coefficient of thermal expansion, making it resistant to thermal shock.
- Recall other common additives: To modify its properties further, other oxides are typically added in smaller proportions. These often include alkali oxides and alkaline earth oxides.
- Consider the specific properties of Pyrex: Pyrex is a well-known brand of borosilicate glass. Its composition is designed to enhance its durability, chemical resistance, and thermal shock resistance.
- Evaluate the options based on common glass compositions:
- Aluminium oxide (\(\text{Al}_2\text{O}_3\)) is often added to improve durability and chemical resistance.
- Sodium oxide (\(\text{Na}_2\text{O}\)) is a common flux in glassmaking, helping to lower the melting point and improve workability, even in borosilicate glass, though in smaller amounts than in soda-lime glass.
- Compare with the given options: Option C mentions a small proportion of aluminium oxide and sodium oxide, which aligns with the known composition of borosilicate glass like Pyrex.
Correct Option:
C) A small proportion of aluminium oxide and sodium oxide
Borosilicate glass, such as Pyrex, is indeed composed primarily of silica (\(\text{SiO}_2\)) and boric oxide (\(\text{B}_2\text{O}_3\)). Additionally, it contains small amounts of other oxides to fine-tune its properties. Aluminium oxide (\(\text{Al}_2\text{O}_3\)) enhances its durability and chemical resistance, while sodium oxide (\(\text{Na}_2\text{O}\)) acts as a flux, aiding in processing, though in much smaller quantities compared to soda-lime glass. These components contribute to the glass's overall strength, thermal stability, and chemical inertness, making it suitable for laboratory apparatus.
Incorrect Options
- A) Potassium chlorate — Potassium chlorate is a chemical compound used as an oxidizer, not a common constituent of glass. Glass compositions typically involve oxides.
- B) Cerium oxide only — Cerium oxide (\(\text{CeO}_2\)) is sometimes used in glass as a decolorizer or for UV absorption, but it is not a primary or essential component alongside silica and boric oxide in typical borosilicate glass like Pyrex. It's also usually not the only other significant additive.
- D) A large proportion of lead oxide — Lead oxide (\(\text{PbO}\)) is a major component of lead glass (crystal glass), which is known for its high refractive index and density. However, lead glass has a low thermal shock resistance and is not used for laboratory apparatus. Borosilicate glass is specifically designed to be lead-free for its thermal and chemical properties.
12.
The main reason Pyrex glass is preferred for laboratory glassware is its:
B.
High solubility in water
C.
High electrical conductivity
D.
Low coefficient of thermal expansion
ANSWER :
D. Low coefficient of thermal expansion
Approach
The question asks why Pyrex glass is preferred for laboratory glassware. This requires understanding the properties of Pyrex and the demands of laboratory environments, particularly concerning temperature changes.
Step-by-step
- Identify the primary challenge in laboratory glassware: Laboratory experiments often involve heating, cooling, and rapid temperature changes. Ordinary glass can crack or shatter under such thermal stress due to expansion and contraction.
- Consider the properties of Pyrex: Pyrex (a type of borosilicate glass) is known for its excellent resistance to thermal shock. This property is directly related to its coefficient of thermal expansion.
- Relate thermal expansion to thermal shock resistance: Materials expand when heated and contract when cooled. If a material has a high coefficient of thermal expansion, it will undergo significant dimensional changes with temperature fluctuations. If different parts of a glass object heat or cool at different rates, the differential expansion or contraction creates internal stresses. If these stresses exceed the material's strength, it will crack.
- Evaluate Pyrex's coefficient of thermal expansion: Pyrex has a significantly lower coefficient of thermal expansion compared to common soda-lime glass. This means it expands and contracts much less for a given temperature change, thus minimizing internal stresses and making it highly resistant to thermal shock.
- Conclude the main reason: The low coefficient of thermal expansion is the fundamental property that allows Pyrex to withstand rapid and extreme temperature changes without breaking, making it ideal for laboratory use where heating and cooling are common.
Correct Option:
D) Low coefficient of thermal expansion — Pyrex, a borosilicate glass, is specifically engineered to have a very low coefficient of thermal expansion. This property means it expands and contracts minimally when subjected to temperature changes. In a laboratory setting, glassware is frequently heated over burners or cooled in ice baths. A low coefficient of thermal expansion prevents the glass from experiencing significant internal stresses due to uneven heating or rapid temperature shifts, thereby preventing it from cracking or shattering. This makes it highly resistant to thermal shock, which is crucial for safety and reliability in experiments.
Incorrect Options
- A) Bright colour — The color of glassware (whether clear or tinted) is generally not a primary functional requirement for most laboratory applications, although amber glass is used for light-sensitive chemicals. Pyrex is typically clear, and its color has no bearing on its thermal properties or suitability for general lab use.
- B) High solubility in water — High solubility in water would be a detrimental property for laboratory glassware, as it would lead to the dissolution of the glass itself and potential contamination of solutions. Pyrex, like most glasses, has very low solubility in water and good chemical resistance, which is a desirable trait, but not the main reason for its preference over other glasses for thermal applications.
- C) High electrical conductivity — Glass is generally an electrical insulator, not a conductor. High electrical conductivity would be undesirable for most laboratory applications, especially those involving electrical measurements or heating elements, as it could pose safety risks or interfere with experiments. Pyrex is an electrical insulator.
