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Class X science isn't as tough as you think. So, which is THE most important chatper in your textbook? What is benzene?
These were some of the questions asked by stressed students during a live chat with Topper Chemistry Expert Amarpreet Kaur on March 26.
Here are the answers to these questions and more!
Deepitapai: What is meant by denatured alcohol?
Amarpreet Kaur: To prevent the misuse of ethanol produced for industrial use, it is made unfit for drinking purposes by adding methanol. Dyes are also added to colour it blue. This is called denatured alcohol.
Sauhard: Please tell what is decarboxylation reaction?
Amarpreet Kaur: Decarboxylation reactions are those reactions in which carbon dioxide is removed.
Deepitapai: A housewife wanted her house to be whitewashed. She bought 10 kg of quick lime from the market and dissolved it in 30 litres of water. On adding lime to water she noticed that the water started boiling even when it was not being heated. Give reason for her observation. Write the corresponding chemical equation and name the product formed.
Amarpreet Kaur: This is because lime when dissolved in water gives calcium hydroxide. This reaction is highly exothermic. So, a large amount of heat is evolved during the reaction Chemical equation: CaO + H2O .......> Ca(OH)2. The product is calcium hydroxide, also known as slaked lime.
Prasanthdj: Do we need to read the orange boxes in the text book
Amarpreet Kaur: Some extra interesting material is placed in light orange boxes in the text book for your knowledge. You will not be asked questions from these. Refer to mock papers
Ishy93: I want an answer from u mam i read this question in some book and its answer was not given. Why CaSO4.1/2H20 is called plaster of paris? How is it possible to have halfwater molecule attached to CaSO4 ?
Amarpreet Kaur: The formula of plaster of paris is CaSO4.1/2H2O. It is written in this form because 2 formula units of CaSO4 share one molecule of water. You can solve these problems to practice.
Aishwarya: Mam I want to know that if we will be asked to balance the equation?
Amarpreet Kaur: Yes, you can be asked to balance the chemical equations. Try solving mock papers.
Swati: What benzene actually is?
Amarpreet Kaur: Benzene is an aromatic organic compound having the formula C6H6.
MOIZ AKHTAR: Sir\Mam. What we mean by heteroatoms?
Amarpreet Kaur: Some organic compounds contain atoms besides carbon and hydrogen. These are heteroatoms. Examples of heteroatoms are nitrogen, oxygen and sulphur. For reference check solved board exam papers.
Priyank: How many questions will be from chemistry in the paper?
Amarpreet Kaur: Number of questions from chemistry will vary but the weightage of the complete unit will remain same. The unit for chemistry in the syllabus is chemical substances, which are alotted a total of 18 marks. Solve these mock papers.
Srinidhi: Dear ma'am what is a carbon compound basically?
Amarpreet Kaur: Carbon compounds are compounds which contain carbon atoms. These are also called organic compounds. There are a vast number of carbon compounds possible due to catenation and tetravalency.
Sanket: What are hygroscopic or deliquescent substances?
Amarpreet Kaur: Hygroscopic substances are those substances which absorb water vapour from air. Some hygroscopic substances, not only absorb moisture from the air, but also dissolve themselves in that moisture leading to a change of state. These are called deliquescent substances.
Diana Abraham C: Should we actually do the hit and trial method to balance equations?
Amarpreet Kaur: First you try balancing the equation bytrial and error method. But if you are unable to balance the equation, then identify the compound which contains the largest number of atoms and in that start balancing the element which has the maximum number of atoms.
Meghana: Mam,what are hydronium ions?does H+(aq) mean the same?
Amarpreet Kaur: Hydronium ion is H3O+. It is formed when H+ ion reacts with H2O. H+ ion is hydrogen ion and not hydronium ion. Hydrogen ion after reacting with water form hydronium ions. Refer to mock papers.
Monisha: Hi.... i have a problem with the addition reaction and the use of catalyst in the chapter carbon and its compounds
Amarpreet Kaur: Addition reactions are those reactions in which two or molecules combine to form a larger single product. A + B gives C. In organic chemistry, addition reactions are a charateristic of unsaturated hydrocarbons like alkenes and alkynes. Hydrogentaion is an example of addition reaction. Catalysts are those substances which do not take part in the reaction but can make the reaction faster.
They are written above the arrow in a chemical reaction. You should mention the catalysts for all the reactions asked in the exams. Refer to these sample videos.
Sauhard: Maam please tell how can etanol and ethanoic acid can be differentiated on the basis of physical and chemical properties
Amarpreet Kaur: Ethanol reacts with sodium and gives sodium ethoxide and liberates hydrogen gas. Whereas Ethanoic acid will not liberate hydrogen gas with sodium.
Sauhard: Maam please tell how can etanol and ethanoic acid can be differentiated on the basis of physical and chemical properties.
Amarpreet Kaur: Ethanol reacts with sodium and gives sodium ethoxide and liberates hydrogen gas. Whereas Ethanoic acid will not liberate hydrogen gas with sodium.
Swati: Cleansing action of soap and detergent is not at all cleared.Pls help
Amarpreet Kaur: Soaps are molecules which have two different ends -- 1. a long hydrocarbon chain called hydrophobic end (water repelling end), 2. the ionic part which is hydrophillic end (water loving). The ionic end of soap is towards water and hydrocarbon part is towards dirt. Micelles are formed. When water is agitated, the micelles are removed and the cloth becomes clean.
Swati: What's the colour of ZnSO4?
Amarpreet Kaur: It is white in colour.
Aishwarya: Where we can find checker box in our text book?
Amarpreet Kaur: Dear A, the Checker box or Punnett square is a diagram that is used to represent/predict the outcome of a particular genetic cross or breeding experiment. So, the genetic cross given at NCERT pg 144 and pg 145 can be represented using Checker box.
Aakanksha: Mam please answer my question soon. Distinguish between alcohol and acetic acid on the basis of physical prop by an activity.
Amarpreet Kaur: Dip both of these solutions in blue litmus paper. Acetic acid will turn blue litmus paper red while alcohol will not.
Meghana: Why distilled water doesn’t conduct electricity?
Amarpreet Kaur: Distilled water is pure water. It does not have any other ions or species besides water. Water is a weak electrolyte and do not conduct electricity.
Snigdha Parthan: Ma'am, when two elements and their valencies are mentioned, how do we know whether they would make an ionic or covalent bond?
Amarpreet Kaur: Ionic compounds are formed when one element has the valence electrons 1, 2, 3 and the second one has 5, 6, 7. Covalent compounds are formed for those elements which have a valency of 4, or both have 5, 6, 7 valence electrons.
Akshay: What is a allotrope?
Amarpreet Kaur: Allotropes are the different chemical modifications of an element which differ in their properties. For example: Carbon has allotropes like Graphite and diamond.
Diana Abraham C: Ma'am can u please tell the chemical names of quick lime, slaked lime and lime water?
Amarpreet Kaur: Quick lime is CaO calcium oxide Slaked lime is Ca(OH)2 calcium hydroxide lime water is saturated calcium hydroxide solution. Its formula is Ca(OH)2
Shohinmukherjee: It is being taught that concentration of h+aq ions decreases when an acid is dilutaed, but i thaught than in case of weak bases it increases because its dissociation increases on adding more water . Explain?
Amarpreet Kaur: When an acid is diluted, the concentration of H+ ions decreases because the dissociation is suppressed. In case of weak bases, the concentration of OH- ions decreases. Get your Fundas right!
All the best.
Shohinmukherjee: Explain the nature of the covalent bond using the bond formation in CH3CL(pls explain keepin in mind 10th syllabus, not polarity)
Amarpreet Kaur: Covalent bonds are formed by sharing of electrons between two atoms. CH3Cl has four single covalent bonds. The first one is between C and H, the second one is between C and second H, the thirs one is between C and third H and the fourth one is between C and Cl. Since Cl has 7 electrons in its valence shell. So, it needs one electron to complete its octet. Practise solved board exam papers.
Vatsal agarwal: What is the difference b/w roasting and calcination. Also, what is benzene?
Amarpreet Kaur: Calcination is the process of heating the concentrated ore in the absence of air while roasting is the heating of concentrated ore in the free supply of air. Benzene is C6H6.
