Physical and Chemical Changes, Solution

When 10 g of calcium carbonate is decomposed completely, then 5.6 g of calcium oxide is formed along with the generation of carbon dioxide. Mass of the carbon dioxide formed is:

[amp_mcq option1=”4.4 g” option2=”5.6 g” option3=”4.6 g” option4=”4.8 g” correct=”option1″]

The mass of the carbon dioxide formed is 4.4 g.

According to the Law of Conservation of Mass, the total mass of the reactants in a chemical reaction is equal to the total mass of the products. In this decomposition reaction, Calcium Carbonate (CaCO₃) decomposes into Calcium Oxide (CaO) and Carbon Dioxide (CO₂).

Given: Mass of reactant (CaCO₃) = 10 g. Mass of one product (CaO) = 5.6 g. Let the mass of the other product (CO₂) be ‘m’. Applying the Law of Conservation of Mass: Mass of CaCO₃ = Mass of CaO + Mass of CO₂. 10 g = 5.6 g + m. m = 10 g – 5.6 g = 4.4 g.

The dye in black ink can be separated by the method of:

[amp_mcq option1=”evaporation” option2=”fractional distillation” option3=”dialysis” option4=”chromatography” correct=”option4″]

The dye in black ink can be separated by the method of chromatography.

Black ink is typically a mixture of several different coloured dyes. Chromatography is a technique used to separate components of a mixture based on their differential partitioning between a stationary phase and a mobile phase. Different dyes in the ink travel at different rates through the stationary phase (like paper), causing them to separate.

Evaporation is used to separate a soluble solid from a liquid. Fractional distillation separates liquids with different boiling points. Dialysis separates particles based on size using a semipermeable membrane. Chromatography is the standard method for separating different coloured dyes in ink.

Which one of the following is NOT an example of colloids?

[amp_mcq option1=”Milk” option2=”Jelly” option3=”Tincture of iodine” option4=”Fog” correct=”option3″]

Tincture of iodine is NOT an example of a colloid; it is a true solution.

A colloid is a heterogeneous mixture where the solute particles are dispersed uniformly throughout the solvent. The particle size in colloids is typically between 1 nm and 1000 nm. True solutions have particle sizes smaller than 1 nm.

Milk is an emulsion (liquid dispersed in liquid). Jelly is a gel (solid dispersed in liquid). Fog is an aerosol (liquid dispersed in gas). All of these are types of colloids. Tincture of iodine is a solution of iodine in alcohol, where iodine dissolves completely forming a homogeneous mixture at the molecular level.

Number of states of matter known so far is:

[amp_mcq option1=”3″ option2=”4″ option3=”5″ option4=”6″ correct=”option3″]

The number of states of matter commonly known and taught in a general science context is considered to be 5.

The three classical states of matter are Solid, Liquid, and Gas. Beyond these, Plasma is widely recognized as a fourth state, and the Bose-Einstein Condensate (BEC) is considered a fifth state.

Plasma is an ionized gas existing at high temperatures. BEC is formed at temperatures near absolute zero. Other states of matter exist under extreme conditions (e.g., neutron-degenerate matter), but 5 is the most common answer when these options are presented.

Which one of the following statements is correct about camphor and ammonium chloride?

[amp_mcq option1=”Both of them are inorganic compounds” option2=”Both of them are organic compounds” option3=”Both of them undergo sublimation” option4=”Camphor is an element but ammonium chloride is a compound” correct=”option3″]

Both camphor and ammonium chloride undergo sublimation.

Sublimation is the process where a substance transitions directly from the solid to the gas state, without passing through the liquid state. Both camphor and ammonium chloride exhibit this property under appropriate conditions.

Camphor (C₁₀H₁₆O) is an organic compound. Ammonium chloride (NH₄Cl) is an inorganic compound. Therefore, statements A, B, and D are incorrect. Camphor sublimes readily at room temperature, while ammonium chloride sublimes upon heating.

At a given temperature and pressure, the force of attraction among the molecules will be highest in case of:

[amp_mcq option1=”helium” option2=”sugar” option3=”water” option4=”carbon tetrachloride” correct=”option2″]

At a given temperature and pressure, the state of matter (solid, liquid, gas) is determined by the strength of the intermolecular forces compared to the thermal energy of the molecules. Solids have the strongest intermolecular forces, holding molecules in fixed positions. Liquids have weaker forces than solids, allowing molecules to move past each other but still keeping them relatively close. Gases have very weak forces, allowing molecules to move freely and far apart. At room temperature and pressure: Helium is a gas, Water and Carbon tetrachloride are liquids, and Sugar is a solid. Therefore, sugar, being in a solid state, will have the highest force of attraction among its molecules compared to the liquids and the gas listed.

The state of matter (solid, liquid, gas) reflects the strength of intermolecular forces. Solids have the strongest forces, liquids have intermediate forces, and gases have the weakest forces. Sugar is a solid at room temperature and pressure, while the other substances are liquids or gases.

Intermolecular forces include London dispersion forces, dipole-dipole forces, and hydrogen bonding. Sugar molecules (like sucrose) are polar and can form extensive hydrogen bonds, in addition to other forces, resulting in a strong lattice structure in the solid state. Helium, a noble gas, only has very weak London dispersion forces. Water has strong hydrogen bonding, but it’s a liquid at room temperature. Carbon tetrachloride is a nonpolar molecule with only London dispersion forces, existing as a liquid.