Question 12 Marks
Why are carbon and its compounds used as fuels for most applications?
Answer
View full question & answer→Carbon and its compounds are used as fuels because they burn in air releasing a lot of heat energy.
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Question 22 Marks
Give a test that can be used to differentiate chemically between butter and cooking oil.###Give a test that can be used to differentiate between saturated and unsaturated hydrocarbons.
Answer
View full question & answer→A bromine water test can be used to chemically differentiate between butter (Saturated) and cooking oil (Unsaturated).
Take two test tubes, one with a small amount of butter in it and the other with some cooking oil. Add bromine water to both the test tubes.
Observation:
Take two test tubes, one with a small amount of butter in it and the other with some cooking oil. Add bromine water to both the test tubes.
Observation:
- Cooking oil decolourises bromine water indicating that it is an unsaturated compound.
- Butter does not decolourise bromine water indicating that it is a saturated compound.
Question 32 Marks
Explain the formation of scum when hard water is treated with soap.
Answer
View full question & answer→When soap is used for washing clothes with hard water, a large amount of soap in water reacts with the calcium and magnesium ions of hard water to form an insoluble precipitate called scum. This makes the cleaning of clothes difficult.
Question 42 Marks
Mention the essential material (chemicals) to prepare soap in the laboratory. Describe in brief the test of determining the nature (acidic/alkaline) of the reaction mixture of saponification reaction.
Answer
View full question & answer→Soap is prepared by heating animal fat or vegetable oil with concentrated sodium hydroxide.
$\text{Fat or oil} + \text{NaOH} \xrightarrow{\text{heat}} \text{Soap} + \text{Glycerol}.$
The process of making soap by the hydrolysis of fats and oils with alkalis is called Saponification.Raw Materials required for preparation of soap in Laboratory:
Vegetable oil, Sodium Hydroxide, Common salt, Beaker, Bunsen burner. TEST: soaps are mostly basic in nature and we can do litmus test red litmus will turn to blue.Question 52 Marks
When you add sodium hydrogen carbonate to acetic acid in a test tube, a gas liberates immediately with a brisk effervescence. Name this gas. Describe the method of testing this gas.
Answer
View full question & answer→Sodium hydrogen carbonate on reaction with acetic acid releases carbon dioxide gas.
NaHCO3 + CH3COOH → CH3COONa + H2O + CO2
Test for carbon dioxide:
The presence of carbon dioxide can be tested by bringing a burning splinter near the mouth of the cylinder containing carbon dioxide - it gets extinguished.
If carbon dioxide is passed through limewater, it turns milky white.
Ca(OH)2 + CO2 → CaCO3 + H2O
NaHCO3 + CH3COOH → CH3COONa + H2O + CO2
Test for carbon dioxide:
The presence of carbon dioxide can be tested by bringing a burning splinter near the mouth of the cylinder containing carbon dioxide - it gets extinguished.
If carbon dioxide is passed through limewater, it turns milky white.
Ca(OH)2 + CO2 → CaCO3 + H2O
Question 62 Marks
A student adds a spoon full of powdered sodium hydrogen carbonate to a flask containing ethanol acid. List two main observations, he must note in his note book, about the reaction that takes place. Also write chemical equation for the reaction.
Answer
View full question & answer→Sodium hydrogen carbonate is the base which on reaction with acid gives brisk effervescence. Also, a colorless and odorless gas is evolved.
The chemical reaction is given as;
$\text{CH}_{3}\text{COOH} +\text{NaHCO}_{3} \rightarrow\text{CH}_{3}\text{COOONa} + \text{H}_{2}\text{O} +\text{CO}_{2}.$
The chemical reaction is given as;
$\text{CH}_{3}\text{COOH} +\text{NaHCO}_{3} \rightarrow\text{CH}_{3}\text{COOONa} + \text{H}_{2}\text{O} +\text{CO}_{2}.$
Question 72 Marks
Write the name and molecular formula of an organic compound having its name suffixed with ‘- ol’ and having two carbon atoms in the molecule. With the help of a balanced chemical equation indicate what happens when it is heated with excess of conc. H2SO4 .
Answer
View full question & answer→Molecular formula: CH3-CH2-OH and name: Ethanol. When it is heated with an excess of conc. Sulphuric acid elimination of water molecule takes place to give ethane.
$\text{C}_2\text{H}_5\text{OH}+\text{H}_2\text{SO}_4\xrightarrow{\Delta}\text{CH}_2=\text{CH}_2+\text{H}_2\text{O}+\text{H}_2\text{SO}_4$
Question 82 Marks
What happens when wood is burnt in a limited supply of oxygen? Name the residue left behind after the reaction and state two advantages of using this residue as a fuel over wood.
Answer
View full question & answer→The wood is burnt in the limited supply of air to obtain charcoal. When wood is burnt in the limited supply of oxygen, water and volatile materials are removed and charcoal is left behind as the residue.
Charcoal is considered a better fuel than wood because:
- It has higher heat generation efficiency.
- It produces less smoke.
- It leaves very less residue behind.
Question 92 Marks
What do you observe when you drop a few drops of acetic acid to a test tube containing:
- Phenolphthalein.
- Distilled water.
- Universal indicator.
- Sodium hydrogen carbonate powder.
Answer
View full question & answer→Acetic acid is a weak acid. The following changes will occur when a few drops of acetic acid are added to the given solutions:
- Phenolphthalein remains colorless, as acetic acid shows a change in colour in basic substances.
- Acetic acid dissolved in water.
- Acetic acid turns the colour of the universal indicator to pale orange.
- When added to sodium hydrogen carbonate powder, acetic acid causes effervescence because of the evolution of carbon dioxide gas in the process.
Question 102 Marks
List two observations which you make when you add a pinch of sodium hydrogen carbonate to acetic acid in a test tube. Write chemical equation for the reaction that occurs.
Answer
View full question & answer→When a pinch of sodium hydrogen .carbonate is added to acetic acid in a test tube, two observations are made.
- Brisk effervescence.
- Evolution of a colorless and odorless gas which is CO2.
CH3COOH(aq) + NaHCO3(s) + CH3COONa(aq) + H2O(i) + CO2(g)
Question 112 Marks
You are provided with as organic compound having the molecular formula, C2H6. Give the name and formula of the compound formed when:
One H atom of C2H6 is replaced by a CHO group.
Answer
View full question & answer→C2H5CHO- propionaldehyde, propanal
Question 122 Marks
Write two points of difference in the structures of diamond and graphite.
Answer
View full question & answer→Diamond:
- Each carbon atom is linked to four other carbon atoms.
- A diamond crystal has a tetrahedral arrangement of carbon atoms.
Graphite:
- Each carbon atom is joined to only three other carbon atoms.
- A graphite crystal has flat hexagonal rings structure.
Question 132 Marks
Write three difference between soaps and detergents.
Answer
View full question & answer→Soaps | Sodium metal | ||
1. | Soap are made from fat and alkali by specification method. | 1. | Detergents are carbonic compounds which are not alkaline. |
2. | There are cheap. | 2. | They are costly. |
3. | There are not suitable for delicate clothes. | 3. | They are suitable for delicate clothes. |
4. | They are clean better in hot water. | 4. | They clean both in hot and cold water. |
5. | They don’t produce lather with hard water and are not able to clean the cloth. | 5. | They clean the cloth even in hard water. |
Question 142 Marks
Write three common functional groups present in organic compounds. Give their symbols /formulae.
Answer
View full question & answer→- Halo group: -X
- Alcohol group: -OH
- Aldehyde group: -CHO
Question 152 Marks
Write the names and structural formulae of all the possible isomers of hexane.
Question 162 Marks
Write the names and formulae for the first three members of the homologous series of chloroalkanes.
Answer
View full question & answer→Chloromethane: CH3Cl
Chloroethane: C2H5Cl
Chloropropan: C3H7Cl
Chloroethane: C2H5Cl
Chloropropan: C3H7Cl
Question 172 Marks
Write the molecular formula of:
- An alkane.
- An alkene.
- An alkyne, each having 20 carbon atoms?
Answer
View full question & answer→- An alkane comprising 20 atoms of carbon (n = 20):
C20H2×20 + 2 = C20 H42
- An alkene comprising 20 atoms of carbon (n = 20):
C20H20×2 = C20H40
- An alkyne comprising 20 atoms of carbon (n = 20):
C20H2×20-2 = C20H38
Question 182 Marks
Write the molecular formula and structure of cyclohexane. How many covalent bonds are there in a molecule of cyclohexane?
Answer
View full question & answer→Molecular formula of cyclohexane is C6H12.
Question 192 Marks
Write the molecular and structural formula of a cyclic hydrocarbon whose molecule contains 8 atoms of carbon.
Answer
View full question & answer→Molecular formula: C8H16
Question 202 Marks
Write the IUPAC name of:
-
$\text{CH}_3\text{COCH}_2\text{CH}_3$
-
$\text{CH}_3-\text{CH}-\text{CH}_3\\ \ \ \ \ \ \ \ \ \ \ |\\ \ \ \ \ \ \ \ \ \text{OH}$
-
$\text{HCOOH}$
-
$\text{CH}_3\text{COOCH}_3$
Answer
View full question & answer→- Butanone
- Propan-2-ol
- Methanoic acid
- Methyl ethanoate
Question 212 Marks
Write the covalent bonding in nitrogen.
Answer
View full question & answer→Nitrogen is a non-metal.A nitrogen atom has 5 electrons in its outer shell.Nitrogen is in group 5 of the periodic table.
Two nitrogen atoms will each share three electrons to form three covalent bonds and make a nitrogen molecule (N2).
This is a picture of a nitrogen molecule.
By sharing the six electrons where the shells touch each nitrogen atom can count 8 electrons in its outer shell.
These full outer shells with their shared electrons are now stable.
The N2 molecule will not react further with other nitrogen atoms.
Question 222 Marks
Write:
- Structural formula.
- Electron-dot structure, of any one isomer of n-heptane(C7H16).
Question 232 Marks
Write names and formulae of hydrocarbons containing a single and a double bond (one example for each). Give one characteristic chemical property of each.
Answer
View full question & answer→- Single bond: Methane, CH4. They are quite unreactive hence they undergo substitution reaction with chlorine in presence of sunlight.
- Double bond: Ethene, CH2 = CH2. They undergo addition reaction in the presence of a catalyst like nickel or palladium.
Question 242 Marks
Write down the structures and names of two isomers of butane (C4H10).
Question 252 Marks
Why soap solution appears cloudy?
Answer
View full question & answer→Soap is mixed with water to form micelle which gives the solution a cloudy appearance when soap is added to the water the fatty acid ionizes. The polar water soluble gets attracted to water while the non-polar tails attract each other. Then the ions are attracted to each other and form the special clusters and sometimes in a form of emulsions which gives a cloudy look.
Question 262 Marks
Why is the conversion of ethanol to ethanoic acid an oxidation reaction?
Answer
View full question & answer→The conversion of ethanol into ethanoic acid is called an oxidation reaction because oxygen is added to it during this conversion.
$\text{CH}_3\text{CH}_2\text{OH}+2[\text{O}]\xrightarrow[]{\ \ \ \ \ \ \ \ \ \ }\text{CH}_3\text{COOH}+\text{H}_2\text{O}\\\text{Ethanol}\ \ \ \ \ \ \ \ \ \ \ \text{Nascent}\ \ \ \ \ \text{Ethanoic acid}\ \ \text{Water}\\\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \text{Oxygen}$
Question 272 Marks
Why is soap not suitable for washing clothes when the water is hard?
Answer
View full question & answer→When soap is used for washing clothes with hard water, a large amount of soap in water is reacting with the calcium and magnesium ions of hard water to form an insoluble precipitate called scum, before it can be used for the real purpose of washing.
Question 282 Marks
Why is graphite a good conductor of electricity but diamond is a non-conductor of electricity?
Answer
View full question & answer→Due to the presence of free electrons in a graphite crystal, it conducts electricity however; a diamond crystal does not have free electrons so it does not conduct electricity.
Question 292 Marks
Why is common salt (sodium chloride) added during the preparation of soap?
Answer
View full question & answer→Common salt is added to the mixture to make the soap come out of solution. Though most of the soap separates out on its own but some of it remains in solution. Common salt is added to precipitate out all the soap from the aqueous solution.
Question 302 Marks
Why have detergents replaced soap as a washing agent?
Answer
View full question & answer→Detergents are better cleansing agents than soaps because they do not form insoluble calcium and magnesium salts with hard water, and hence can be used for washing even with hard water.
Question 312 Marks
Why graphite is smooth?
Answer
View full question & answer→Graphite is a form of crystalline carbon in which each carbon atom is covalently bonded to three other carbon atoms. The carbon atoms are arranged in layers, with strong bonds within each layer but only weak bonds between layers. The weak bonds between layers allow the layers to slide over one another, so graphite is relatively soft and slippery. This makes it useful as a lubricant.
Question 322 Marks
Why does the element carbon from a large number of carbon compounds?
Answer
View full question & answer→Carbon forms a large number of carbon compounds because carbon atoms can link with one another by means of covalent bonds to form long chains of carbon atoms.
Question 332 Marks
Why does ethyne (acetylene) burn with a sooty flame?
Answer
View full question & answer→Ethyne (acetylene) burn with a sooty flame because ethyne is an unsaturated hydrocarbon and the percentage of carbon in these hydrocarbons is comparatively higher which does not get oxidised completely in oxygen of air.
Question 342 Marks
Why covalent compound are volatile in nature with low boiling and low melting point?
Answer
View full question & answer→Covalent compounds have weak forces of attraction between the binding molecules. Thus less energy is required to break the force of bonding. Therefore covalent compounds have low melting and boiling point.
Question 352 Marks
Why compounds like petrol, coal, etc generate heat or light or both on combustion?
Answer
View full question & answer→Examples of fuel include wood, coal, natural gas, and oil.Combustion is where you burn a fuel in the presence of an oxidant like oxygen. Heat is produced, because the bonds in thefuel store more energy than the bonds in the water and carbon dioxide that are the products of combustion. As a result, the bonds present in the molecules of fuel break, releasing energy. Sometimes, the energy released falls in the visible range of the electromagnetic spectrum (which means the energy released is visible to human eye) which we call as light. Sometimes the energy released falls under infrared region, which we commonly call as heat. Basically, the compounds generate heat or light or both due to the release of energy from the breaking of molecular bonds.
Question 362 Marks
Why are vegetable oils healthy as compared to vegetable ghee? How are vegetable oils converted into vegetable ghee? Name the process.
Answer
View full question & answer→- Vegetable oils contain unsaturated fatty acids while vegetable ghee contains saturated fatty acids which are said to be harmful for health.
- Vegetable oils are converted into vegetable ghee by adding hydrogen in the presence of catalysts palladium(Pd) or nickel(Ni).
- The process involved in this is addition reaction (hydrogenation). It is defined as the addition of hydrogen atoms in carbon atoms of an organic compound.
Question 372 Marks
Why are coal and petroleum called fossil fuels?
Answer
View full question & answer→Coal and petroleum are called fossil fuels because they are produced through the decomposition of the pre-historic organisms (plants and animals) buried deep in the soil since millions of years ago.
Question 382 Marks
Which type of synthetic detergents are biodegradable?
Answer
View full question & answer→Branched synthetic detergents are less biodegradable compared to detergents equipped with continuous chain of carbon atoms. Alkyl benzene sulfonates that are continuous chain are known to be completely biodegradable. In addition another continuous chain option called alkyl sulfates such as CH3(CH2)16CH2OSO3Na+ is also bio degradable.
Question 392 Marks
Which of the two is better for washing clothes when the water is hard: soap or detergent? Give reason for your answer.
Answer
View full question & answer→Detergent is better for washing clothes in hard water. They are better cleansing agents than soaps because they do not form insoluble calcium and magnesium salts with hard water, and hence can used for washing even with hard water.
Question 402 Marks
Which of the following hydrocarbons will give substitution reactions and why?
CH4, C3H6, C3H8, C4H6, C5H12, C5H10.
CH4, C3H6, C3H8, C4H6, C5H12, C5H10.
Answer
View full question & answer→CH4, C3H8, C5H12 all these are saturated hydrocarbons (Alkanes) and hence will give substitution reactions.
Question 412 Marks
Which of the following hydrocarbons can decolourise bromine water and which cannot? Why?
C6H12, C6H14, C6H10
C6H12, C6H14, C6H10
Answer
View full question & answer→C6 H12 and C6 H10C a decolourise bromine water since these are unsaturated hydrocarbons.
C6 H14 cannot decolourise bromine water since it is a saturated hydrocarbon.
C6 H14 cannot decolourise bromine water since it is a saturated hydrocarbon.
Question 422 Marks
Which alcohol is used in cough syrups and tonics?
Answer
View full question & answer→Ethanol (C2H5OH) is used in cough syrups and tonics. Ethanol is a good solvent. It is most commonly used in medicines because it is an excellent solvent, which in a sense is better than water to keep the other ingredients dissolved in the right liquid form and it gets diluted in some cough syrups.
Question 432 Marks
What will you observe when dilute ethanoic acid and dilute hydrochloric acid are put on universal indicator paper, one by one? What does it show?
Answer
View full question & answer→Dilute ethanoic acid turns universal indicator paper to orange, showing that its pH is about 4 which tell us that ethanoic acid is a weak acid. On the other hand, dilute hydrochloric acid turns universal indicator paper to red, showing that its pH is about 1. This shows us that hydrochloric acid is a strong acid.
Question 442 Marks
What will be the formula and electron dot structure of cyclopentane?
Question 452 Marks
What is the unique property of carbon atom? How is this property helpful to us?
Answer
View full question & answer→The most unique property of carbon atom is its ability to combine itself, atom to atom to form long chains. This property of self combination is useful to us because it gives rise to an extremely large number of carbon compounds (or organic compounds).
Question 462 Marks
What is the molecular formula and structural formula of a cyclic hydrocarbon whose one molecule contains 8 hydrogen atoms?
Answer
View full question & answer→The molecular formula of a cyclic hydrocarbon is C4H8, as it satisfies the general formula of a cyclic hydrocarbon, i.e. CnH2n. Here, the number of hydrogen atoms is already given as 8, i.e. 2n = 8. Therefore, $\text{n} = \frac{8}{2}=4.$ Here, n represents the number of carbon atoms. Therefore, the molecular formula is C4H8. The structural formula of the cyclic hydrocarbon C4H8 is as follows:
Question 472 Marks
What is the IUPAC name of:
- CH3–CH2–CH=CH2
- CH3CHO?
Answer
View full question & answer→The IUPAC name of the organic compound:
- CH3–CH2–CH=CH2 is But-1-ene or 1-Butene
- CH3CHO is methn-al
Question 482 Marks
What is the effect of drinking methanol?
Answer
View full question & answer→When methanol is consumed, it is oxidised to methanal in the liver. Methanal reacts rapidly with the components of cell, leading to the coagulation of protoplasm. Consumption of methanol can also damage the optic nerve, resulting in blindness.
Question 492 Marks
What is saponification? Write the reaction involved in this process.
Answer
View full question & answer→When ester treated with an alkali, the reaction gives ethanol and sodium ethanoate. This reaction is called saponification reaction because this reaction forms the basis of preparation of soap. This can be given by following equation.
CH3COOC2H5 + NaOH → CH3COONa + C2H5OH
CH3COOC2H5 + NaOH → CH3COONa + C2H5OH
Question 502 Marks
What is saponification? Write the chemical equation of the reaction involved in this process. Name all the substances which take part in this process and also those which are formed.
Answer
View full question & answer→The process of making soap by the hydrolysis of fats and oils with alkalis is called saponification.
$ \underset{\text {(Anester) }}{\text {Factor Oil}} + \underset{\text {(Analkali)}}{ \text {Sodiumhydroxide}} \xrightarrow{\text {Heat}} \underset{\substack{\text { (Sodium salt } \\ \text { of fatty acid)}}} {\text Soap} + \underset{\text {(An alcohol)}} {\text Glyoerol}$
$ \underset{\text {(Anester) }}{\text {Factor Oil}} + \underset{\text {(Analkali)}}{ \text {Sodiumhydroxide}} \xrightarrow{\text {Heat}} \underset{\substack{\text { (Sodium salt } \\ \text { of fatty acid)}}} {\text Soap} + \underset{\text {(An alcohol)}} {\text Glyoerol}$