Chapter: Important Gases
Which one of the following is the colour ofhydrogen gas?
Hydrogen (H2) is the simplest and lightest element in the periodic table, and it is known for being colourless, odourless, and tasteless under standard conditions.
As a diatomic molecule, hydrogen exists naturally as H2. The chemical reaction involved in its formation is:
During combustion, hydrogen reacts with oxygen, producing water, which is a colourless liquid. Observations using hydrogen in experiments show no visible colour change, confirming its colourless nature.
Consider a diagram showing a comparison of various gases, highlighting hydrogen as colourless, alongside gases that exhibit distinct colours.
Verified against NCERT Class 11 Chemistry, Chapter 5 (Classification of Elements and Periodicity in Properties).
Silver artefacts get tarnished in air due to the formation of
The tarnishing of silver is primarily a chemical reaction where silver (Ag) reacts with hydrogen sulfide (H₂S), leading to the formation of silver sulphide (Ag₂S).
The tarnishing process can be represented by the following balanced chemical equation:
Observation: The black coating seen on tarnished silver items is silver sulphide (Ag₂S), indicating a chemical change.
To remember the order of silver tarnishing, think of Sulphide = Silver tarnishing as in the Blackening of silver.
Consider a diagram comparing tarnished and non-tarnished silver artifacts, illustrating the presence of H₂S and resulting black Ag₂S layer formation.
Verified against NCERT Class XI Chemistry, Chapter 1 (Some Basic Concepts of Chemistry).
Liquid vegetable oils are converted to solid margarine by the use of
The transformation of liquid vegetable oils to solid margarine is achieved through hydrogenation, which is an addition reaction where hydrogen gas is added to unsaturated fats, thereby increasing their saturation and altering their physical state.
The hydrogenation process can be represented as follows:
This process often uses a nickel catalyst at elevated temperatures and pressures to facilitate the addition of hydrogen to the double bonds of fatty acids in the oils.
Remember: "H" for Hardening — Hydrogenation hardens oils into margarine.
Consider a flowchart showing the hydrogenation process, with stages detailing the transition from liquid vegetable oil to solid margarine, highlighting the reaction conditions (catalyst, temperature).
Verified against NCERT Class XI Chemistry, Chapter 12 (Organic Chemistry - Some Basic Principles and Techniques).
Match List-I with List-II and select the answerusing the code given below the lists :
Option D is correct. Washing soda is Na2CO3 • 10H2O, Baking soda is NaHCO3, Bleaching powder is CaOCl2, and Gypsum is CaSO4 • 2H2O.
The question requires matching chemical names with their respective chemical formulas. Familiarity with common chemical compounds and their systematic naming conventions aids in selecting the correct match.
Understanding the relationships between common chemical names and their formulas is crucial. Here's a detailed breakdown of the matches:
Remember the key components: Sodium carbonate is washing soda, sodium bicarbonate is baking soda, and calcium hypochlorite is bleaching powder. For gypsum, think of drywall and its hydration.
Understanding the relationship between common product names and their chemical compositions is essential for identifying correct chemical formulas.
A visual chart depicting common household chemicals, their chemical formulas, and uses can help memorize these associations effectively.
Which one of the following is known as ‘water gas’?
Water gas is primarily produced via the reaction of solid carbon with water vapor. This process can be represented by the following reaction:
The reaction occurs at high temperatures (around 1270 K), where the steam reacts with solid carbon (usually sourced from coke), forming a gaseous mixture of carbon monoxide (CO) and hydrogen (H₂). This mixture, known as water gas, is utilized in various industrial processes, including:
Water gas plays a crucial role in chemical industries due to its reactivity and ability to serve as a reducing agent.
Remember: Carbon + H₂O = CO + H₂ (Water Gas) can be simplified to "C-H to C-O & H".
Illustrate the water gas production process in a flow chart showing solid carbon reacting with steam at high temperature to form water gas (CO + H₂). Include arrows indicating the reaction direction and label reactants and products.
Verified against NCERT Class XII Chemistry, Chapter on Hydrocarbons.
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