Carbon and its Compounds: Class 10 Science Practice Questions

Meera works in a food quality testing laboratory. One day, she receives four different liquid samples labelled P, Q, R and S for identification. She is told that each sample is one of the following: ethanol, ethanoic acid, a soap solution, or a detergent solution. She performs a litmus test, a sodium bicarbonate test, and a hard water test on each sample, and records her observations in a table.

Read the following passage carefully and answer the questions that follow:

Meera works in a food quality testing laboratory. One day, she receives four different liquid samples labelled P, Q, R and S for identification. She is told that each sample is one of the following: ethanol, ethanoic acid, a soap solution, or a detergent solution. To identify them, she performs the following tests:

• Test 1 (Litmus test): She dips blue and red litmus paper into each sample.
• Test 2 (Sodium bicarbonate test): She adds a small amount of NaHCO₃ to each sample.
• Test 3 (Hard water test): She adds each sample to hard water (containing Ca²⁺ and Mg²⁺ ions) and shakes the mixture.

Her observations are summarised below:

| Sample | Litmus test | NaHCO₃ test | Hard water test |
|--------|-------------|-------------|------------------|
| P | Turns blue litmus red | Brisk effervescence, colourless gas evolved | Lather forms |
| Q | No change | No change | Lather forms freely, no scum |
| R | No change | No change | Lather forms, but white curdy precipitate forms |
| S | No change | No change | No lather, no precipitate |

(a) Identify sample P and name the gas evolved in the NaHCO₃ test. [1 mark]
(b) Identify sample Q and explain why it forms lather freely even in hard water. [1 mark]
(c) Sample R forms a white curdy precipitate with hard water. Write the chemical equation for this reaction and state one advantage of sample Q over sample R in daily use. [2 marks]
OR
(c) Sample S is ethanol. Meera heats sample S gently with sample P in the presence of a few drops of concentrated H₂SO₄. Name the type of reaction that occurs, write the equation for this reaction, and state the role of concentrated H₂SO₄ in this reaction. [2 marks]

Riya is a Class 10 student who is learning about carbon compounds in her chemistry class. Her teacher shows her four bottles labelled P, Q, R and S containing different organic liquids. She is told the following:

• Bottle P contains a 2-carbon compound with an –OH functional group.
• Bottle Q contains a 2-carbon compound with a –COOH functional group.
• Bottle R contains the product formed when P and Q react together in the presence of conc. H₂SO₄.
• Bottle S contains the product formed when R is treated with NaOH solution.

Riya is a Class 10 student who is learning about carbon compounds in her chemistry class. Her teacher shows her four bottles labelled P, Q, R and S containing different organic liquids. She is told the following:

• Bottle P contains a 2-carbon compound with an –OH functional group.
• Bottle Q contains a 2-carbon compound with a –COOH functional group.
• Bottle R contains the product formed when P and Q react together in the presence of conc. H₂SO₄.
• Bottle S contains the product formed when R is treated with NaOH solution.

Answer the following questions based on the above information:

(a) Identify the compounds in bottles P and Q. Write their IUPAC names and molecular formulae.

(b) Write the balanced chemical equation for the reaction between P and Q that produces R. Name the type of reaction and state the role of conc. H₂SO₄ in this reaction.

(c) Name the compound in bottle S and write the balanced chemical equation for its formation from R. What is this reaction called, and what is its industrial importance?

Priya is working on a science project about everyday food items. She notices that her mother uses baking soda while making pancakes, and the pancakes rise and become fluffy. She also observes that vinegar (a dilute solution of ethanoic acid) is used as a preservative in pickles. Curious about the chemistry involved, she investigates reactions of ethanoic acid and ethanol with different substances.

Priya is working on a science project about everyday food items. She notices that her mother uses baking soda while making pancakes, and the pancakes rise and become fluffy. She also observes that vinegar (a dilute solution of ethanoic acid) is used as a preservative in pickles. Curious about the chemistry involved, Priya decides to investigate.

She takes two test tubes:
- Test tube A: A pinch of baking soda + 2 mL of vinegar
- Test tube B: A piece of sodium metal + 2 mL of ethanol

She observes brisk effervescence in both test tubes and collects the gas evolved in each case.

(a) Identify the gas evolved in Test tube A. Name the type of chemical reaction taking place in it.

(b) Identify the gas evolved in Test tube B. State ONE property that can be used to distinguish the gas in Test tube A from the gas in Test tube B.

(c) Priya then takes a fresh sample of ethanoic acid and adds a few drops of universal indicator to it. She observes the indicator turns orange-red. She also adds a few drops of universal indicator to ethanol and observes it turns green.

Explain why ethanoic acid turns the indicator orange-red while ethanol turns it green. Also write the IUPAC name and one common use of ethanoic acid.

A food chemist is studying the properties of four organic compounds found in common household items. She labels them P, Q, R, and S.

• Compound P is present in vinegar. It has a pungent, sour smell and turns blue litmus red. When sodium carbonate is added to it, brisk effervescence is observed.
• Compound Q is present in alcoholic beverages. It has a pleasant smell and is completely miscible with water. When compound Q is warmed with compound P in the presence of a few drops of concentrated sulphuric acid, a sweet-smelling compound T is formed.
• Compound R is obtained when compound T is boiled with sodium hydroxide solution. The products of this reaction are compound Q and the sodium salt of compound P.
• Compound S is obtained by the dehydration of compound Q using excess concentrated sulphuric acid at 443 K. It decolourises bromine water.

Read the following passage and answer the questions that follow.

A food chemist is studying the properties of four organic compounds found in common household items. She labels them P, Q, R, and S.

• Compound P is present in vinegar. It has a pungent, sour smell and turns blue litmus red. When a small piece of sodium carbonate is added to it, brisk effervescence is observed.
• Compound Q is present in alcoholic beverages. It has a pleasant smell and is completely miscible with water. When compound Q is warmed with compound P in the presence of a few drops of concentrated sulphuric acid, a sweet-smelling compound T is formed.
• Compound R is obtained when compound T is boiled with sodium hydroxide solution. The products of this reaction are compound Q and the sodium salt of compound P.
• Compound S is obtained by the dehydration of compound Q using excess concentrated sulphuric acid at 443 K. It decolourises bromine water.

(a) Identify compounds P and Q. Write their IUPAC names and molecular formulas.
(b) Name the type of reaction that occurs when compound Q reacts with compound P in the presence of concentrated sulphuric acid. Write the balanced chemical equation for this reaction.
(c) Identify compound S. State the structural feature of compound S that allows it to decolourise bromine water, and name the type of reaction involved. OR (c) The chemist notices that compound Q burns with a blue, non-sooty flame, while a higher homologue of Q containing four carbon atoms burns with a slightly sooty flame. Explain why the nature of the flame changes as the carbon chain length increases. Also state one use of compound Q as a fuel.

A student named Priya is working in a chemistry lab. She takes 10 mL of coconut oil in a beaker and adds 30 mL of concentrated NaOH solution to it. She heats the mixture gently while stirring continuously for about 20 minutes. After heating, she adds a large quantity of common salt (NaCl) solution to the mixture and stirs it.

A student named Priya is working in a chemistry lab. She takes 10 mL of coconut oil in a beaker and adds 30 mL of concentrated NaOH solution to it. She heats the mixture gently while stirring continuously for about 20 minutes. After heating, she adds a large quantity of common salt (NaCl) solution to the mixture and stirs it.

Based on this activity, answer the following questions:

(a) Name the type of chemical reaction that takes place when NaOH reacts with coconut oil. Write the general equation for this reaction.

(b) Why does Priya add common salt (NaCl) solution at the end of the activity?

(c) A classmate observes that the soap formed does not lather well when tested with tap water collected from a nearby bore well, but lathers well with distilled water. Explain why this happens. Also suggest ONE advantage of using synthetic detergents over soap in such a situation.

A food scientist is developing a new cooking oil product. She notices that the oil, which contains long-chain unsaturated fatty acids, becomes solid at room temperature after a specific industrial process. She also observes that when a small piece of sodium metal is dropped into ethanol (one of the solvents used in her lab), a brisk effervescence occurs. Later, she tests the cleaning ability of two different products — a soap and a synthetic detergent — in the local hard water supply and records her observations.

A food scientist is developing a new cooking oil product. She notices that the oil, which contains long-chain unsaturated fatty acids, becomes solid at room temperature after a specific industrial process. She also observes that when a small piece of sodium metal is dropped into ethanol (one of the solvents used in her lab), a brisk effervescence occurs. Later, she tests the cleaning ability of two different products — a soap and a synthetic detergent — in the local hard water supply and records her observations.

Based on the above scenario, answer the following questions:

(a) Name the industrial process by which the unsaturated liquid oil is converted into a solid fat. Write the chemical equation for this process using a general unsaturated compound (alkene) as an example.

(b) Identify the gas evolved when sodium reacts with ethanol. Write the balanced chemical equation for this reaction.

(c) The food scientist finds that soap does not lather well in the local hard water, but the synthetic detergent lathers freely. Give TWO reasons to explain this difference in behaviour.

Asha works in a cooking oil factory. Her job is to convert liquid vegetable oils into solid fats (vanaspati ghee) for longer shelf life. The process involves passing hydrogen gas through the liquid oil in the presence of a nickel catalyst. She also notices that when the solid fat is left exposed to air for many days, it develops a bad smell and taste. Her supervisor tells her that the solid fat has undergone a chemical change due to atmospheric oxygen. Asha's factory also makes soap. The soap is made by heating the same vegetable oil with a concentrated sodium hydroxide solution. The resulting soap is then tested in the local water supply, which is known to be hard water containing dissolved calcium and magnesium salts. The soap forms very little lather and a white, curdy substance appears instead.

Read the following passage and answer the questions that follow:

Asha works in a cooking oil factory. Her job is to convert liquid vegetable oils into solid fats (vanaspati ghee) for longer shelf life. The process involves passing hydrogen gas through the liquid oil in the presence of a nickel catalyst. She also notices that when the solid fat is left exposed to air for many days, it develops a bad smell and taste. Her supervisor tells her that the solid fat has undergone a chemical change due to atmospheric oxygen.

Asha's factory also makes soap. The soap is made by heating the same vegetable oil with a concentrated sodium hydroxide solution. The resulting soap is then tested in the local water supply, which is known to be hard water containing dissolved calcium and magnesium salts. The soap forms very little lather and a white, curdy substance appears instead.

(a) Name the type of reaction by which liquid oil is converted into solid fat in Asha's factory.
(b) Name the chemical phenomenon that causes the solid fat to develop a bad smell and taste on prolonged exposure to air.
(c) (i) Name the type of reaction used to make soap from vegetable oil and NaOH. Write a chemical equation to represent this reaction (you may use RCOOH to represent the fatty acid part of the oil).
(ii) Explain why the soap forms little lather and produces a white, curdy substance in the local hard water supply.

A food technology student, Priya, is working on extending the shelf life of packaged snacks. She notices that a bag of potato chips left open turns rancid within two days, while a sealed bag of the same chips stays fresh for several months. On reading the label of the sealed bag, she finds it contains 'ethyl ethanoate' as an added flavouring agent and notes that the bag is flushed with nitrogen gas before sealing. Her chemistry teacher explains that the long carbon chains in the fats present in chips are susceptible to a particular chemical change, and that the same organic chemistry principles that govern this change also explain why ethyl ethanoate can be prepared in the laboratory.

A food technology student, Priya, is working on extending the shelf life of packaged snacks. She notices that a bag of potato chips left open turns rancid within two days, while a sealed bag of the same chips stays fresh for several months. On reading the label of the sealed bag, she finds it contains 'ethyl ethanoate' as an added flavouring agent and notes that the bag is flushed with nitrogen gas before sealing. Her chemistry teacher explains that the long carbon chains in the fats present in chips are susceptible to a particular chemical change, and that the same organic chemistry principles that govern this change also explain why ethyl ethanoate can be prepared in the laboratory.

(a) Identify the chemical process by which open chips turn rancid, naming the type of reaction involved. [1 mark]

(b) State ONE reason why the sealed bag is flushed with nitrogen gas before sealing, rather than simply being sealed with air inside. [1 mark]

(c) Priya's teacher says ethyl ethanoate can be prepared from two simpler compounds.
(i) Name the two compounds required and write the balanced chemical equation for this preparation, including the catalyst and the type of reaction. [1 mark]
(ii) Priya notices that when she adds a few drops of sodium carbonate solution to a sample of one of the starting materials used in (c)(i), brisk effervescence is observed. Identify this starting material and write the balanced chemical equation for this reaction. [1 mark]

An oxygen atom has the atomic number 8. How many valence electrons does an oxygen atom possess, and how many covalent bonds can it typically form to complete its octet?

Which of the following functional groups is present in ethanoic acid?

In the formation of a propyne (C₃H₄) molecule, the first and second carbon atoms are joined by a single bond, while the second and third carbon atoms are joined by a triple bond. What is the total number of electrons shared in the entire propyne molecule?

In a molecule of propyne (C₃H₄), the first two carbon atoms are joined by a triple bond, and the third carbon atom is bonded to the second carbon atom by a single bond. How many total electrons are shared in all the covalent bonds present in one molecule of propyne?

In the structure of diamond, each carbon atom is covalently bonded to four other carbon atoms in a rigid three-dimensional network. Which of the following properties of diamond is a direct consequence of this bonding arrangement?

Priya is making salad dressing in the kitchen. She adds vinegar (a dilute solution of ethanoic acid) to olive oil and shakes the bottle. She notices that the vinegar and oil do not mix even after vigorous shaking. Which property of ethanoic acid best explains why it mixes well with water but NOT with olive oil?

The atomic number of sulfur is 16. How many valence electrons does a sulfur atom possess, and how many covalent bonds can it typically form to complete its octet?

2
4
6
8

In a molecule of nitrogen gas (N₂), the two nitrogen atoms are joined by a triple bond, sharing three pairs of electrons. Similarly, in a molecule of ethyne (C₂H₂), the two carbon atoms are also joined by a triple bond. How many total electrons are shared between the two carbon atoms alone in the triple bond of ethyne?

The atomic number of chlorine is 17. How many valence electrons are present in one atom of chlorine, and how many covalent bonds can it typically form to achieve a stable octet configuration?

Ethyne (C₂H₂) is a hydrocarbon used in welding torches. Which of the following correctly describes the type of bond between the two carbon atoms in ethyne and the total number of shared electrons in that bond?

A carbon compound contains 2 carbon atoms, 6 hydrogen atoms, and 1 oxygen atom in its molecular formula. The compound belongs to the homologous series of alcohols. Identify the IUPAC name of this compound.

A student is given two colourless liquids, P and Q. The following observations are recorded:
• Liquid P has a pungent, sour smell and turns blue litmus paper red.
• When P is added to solid sodium hydrogen carbonate, brisk effervescence is observed and the gas produced turns lime water milky.
• Liquid Q is neutral (no effect on litmus), burns with a blue flame, and does not react with sodium hydrogen carbonate.
• When P and Q are heated together in the presence of concentrated H₂SO₄, a sweet-smelling liquid R is produced.
• When R is treated with aqueous NaOH solution on heating, P and Q are regenerated.

Which of the following correctly identifies P, Q, and R, AND correctly names the reaction that converts R back to P and Q?

A carbon compound contains 2 carbon atoms, 6 hydrogen atoms, and 1 oxygen atom in its molecular formula. The compound belongs to the homologous series of alcohols. Identify the compound.

The melting point of pure ethanoic acid is 290 K. Based on this fact, which of the following statements is correct about ethanoic acid?

In the allotrope of carbon known as graphite, each carbon atom is bonded to how many other carbon atoms, and what type of bonding holds the layers together?

Buckminsterfullerene (C₆₀) is an allotrope of carbon in which each carbon atom is covalently bonded to exactly three other carbon atoms, forming a hollow spherical structure. Which of the following statements correctly describes a property of Buckminsterfullerene that distinguishes it from both diamond and graphite?

In a molecule of ethene (C₂H₄), the two carbon atoms are joined by a double bond, and each carbon atom is also bonded to two hydrogen atoms. Which of the following correctly states the total number of single bonds and double bonds present in one molecule of ethene respectively?

A student is given five carbon compounds with the following molecular formulae:
(i) C₂H₄ (ii) C₃H₆ (iii) C₄H₈ (iv) C₅H₁₀ (v) C₆H₁₄

The student adds bromine water to each compound. Which of the following conclusions is CORRECT?

A student draws the structural skeleton of a five-carbon compound. How many structurally different carbon skeletons are possible for an alkane with five carbon atoms (C₅H₁₂)?

In a molecule of acetic acid (CH₃COOH), the carbon atoms, hydrogen atoms, and oxygen atoms are held together by covalent bonds. How many single bonds and double bonds are present in one molecule of acetic acid respectively?

How many valence electrons are present in a phosphorus atom ³¹₁₅P, and how does this compare to the number of covalent bonds carbon (tetravalent) can form?

In the diamond allotrope of carbon, each carbon atom forms covalent bonds with four other carbon atoms. Which of the following correctly explains why diamond is an extremely hard substance?