Chapter 1: Some Basic Concepts of Chemistry Short Questions | chemistry Class 11 CBSE

ByteNotes

Chapter 1: Some Basic Concepts of Chemistry Short Questions | chemistry Class 11 CBSE | ByteNotes.in

Short Answer

Easy difficulty • Direct answer format

Easy

Question 1

Quick Recall

What is matter? State the three physical states of matter.

Matter is anything that has mass and occupies space; all objects around us like water, air, and living beings are made of matter.
The three physical states of matter are solid, liquid, and gas, which differ in the arrangement and freedom of movement of their constituent particles.
Solids have definite shape and volume; liquids have definite volume but no definite shape; gases have neither definite shape nor definite volume.

ByteNotes

Short Answer

Easy difficulty • Direct answer format

Easy

Question 2

Quick Recall

Distinguish between a homogeneous and a heterogeneous mixture with one example each.

A homogeneous mixture has a uniform composition throughout, meaning particles of its components are uniformly distributed in the bulk; example: sugar solution in water.
A heterogeneous mixture has a non-uniform composition, and different components may be visible separately; example: a mixture of salt and sand.
The components of both types of mixtures can be separated by physical methods such as filtration, distillation, or hand-picking.

ByteNotes

Short Answer

Easy difficulty • Direct answer format

Easy

Question 3

Quick Recall

State the Law of Conservation of Mass and name its proposer.

The Law of Conservation of Mass was put forth by Antoine Lavoisier in 1789 based on careful experiments on combustion reactions.
The law states that in all physical and chemical changes, there is no net change in mass; matter can neither be created nor destroyed.
This law implies that the total mass of reactants equals the total mass of products in any chemical reaction.

ByteNotes

Short Answer

Medium difficulty • Direct answer format

Medium

Question 4

Quick Recall

Define atomic mass unit. What is 1 amu equal to in grams?

One atomic mass unit (amu or u) is defined as a mass exactly equal to one-twelfth of the mass of one carbon-12 atom.
1 amu = 1.66056 × 10-24 g, and the present system of atomic masses is based on carbon-12 as the standard, agreed upon in 1961.
At present, 'amu' has been replaced by 'u', known as unified mass, and 12C is assigned a mass of exactly 12 u.

ByteNotes

Short Answer

Easy difficulty • Direct answer format

Easy

Question 5

Quick Recall

What is the mole? State the value of Avogadro's constant.

The mole is the SI unit of amount of substance; one mole contains exactly 6.02214076 × 1023 elementary entities such as atoms, molecules, or ions.
The Avogadro constant (NA) = 6.022 × 1023 mol-1; this number is named in honour of Amedeo Avogadro.
The mole concept links the macroscopic mass of a substance to the microscopic number of particles it contains.

ByteNotes

Short Answer

Medium difficulty • Direct answer format

Medium

Question 6

Quick Recall

State Gay Lussac's Law of Gaseous Volumes with an example.

Gay Lussac's Law (1808) states that when gases combine or are produced in a chemical reaction, they do so in a simple whole-number ratio by volume, provided all gases are at the same temperature and pressure.
Example: 100 mL of hydrogen combines with 50 mL of oxygen to give 100 mL of water vapour; the volume ratio H2:O2:H2O = 2:1:2.
This law is essentially the law of definite proportions applied to volumes of gases and was later explained by Avogadro's work in 1811.

ByteNotes

Short Answer

Medium difficulty • Direct answer format

Medium

Question 7

Quick Recall

Define significant figures. How many significant figures are present in 0.0052 and 2.005?

Significant figures are meaningful digits in a measurement that are known with certainty plus one uncertain (estimated) digit; they indicate the precision of a measurement.
In 0.0052, there are two significant figures (5 and 2); the leading zeros only indicate the position of the decimal point and are not significant.
In 2.005, there are four significant figures; zeros between non-zero digits are always significant.

ByteNotes

Short Answer

Medium difficulty • Direct answer format

Medium

Question 8

Quick Recall

Distinguish between precision and accuracy in measurement.

Precision refers to the closeness of various measurements of the same quantity to each other; precise measurements are reproducible but not necessarily correct.
Accuracy is the agreement of a particular measured value with the true value of the result; an accurate measurement is close to the actual correct value.
A set of measurements can be precise but not accurate (e.g., results of 1.95 g and 1.93 g when true value is 2.00 g), or both precise and accurate (e.g., 2.01 g and 1.99 g).

ByteNotes

Short Answer

Medium difficulty • Direct answer format

Medium

Question 9

Quick Recall

State the Law of Definite Proportions. Who proposed it?

The Law of Definite Proportions was given by French chemist Joseph Proust; it states that a given compound always contains exactly the same proportion of elements by weight, regardless of its source.
Proust demonstrated this using natural and synthetic cupric carbonate samples, both of which contained copper, carbon, and oxygen in the ratio 51.35:9.74:38.91 by mass.
This law is also known as the Law of Definite Composition; it forms the basis for identifying pure compounds.

ByteNotes

Short Answer

Medium difficulty • Direct answer format

Medium

Question 10

Quick Recall

What is dimensional analysis? Illustrate with one example.

Dimensional analysis (also called the factor label method or unit factor method) is a technique used to convert a quantity from one system of units to another by multiplying with appropriate unit factors.
A unit factor is a ratio equal to 1 formed from a known equivalence, e.g., since 1 in = 2.54 cm, the unit factor is (2.54 cm / 1 in).
Example: Length of 3 inches = 3 in × (2.54 cm / 1 in) = 7.62 cm; units cancel like algebraic quantities, leaving the desired unit.

ByteNotes

Short Answer

Medium difficulty • Direct answer format

Medium

Question 11

Quick Recall

What is average atomic mass? Why is it used instead of the mass of a single isotope?

Average atomic mass is the weighted mean of the atomic masses of all naturally occurring isotopes of an element, calculated by taking into account their relative abundances (percent occurrence).
It is used because most elements exist as a mixture of isotopes in nature; using only one isotope's mass would not represent the actual element found in the laboratory.
For example, carbon has three isotopes (12C, 13C, 14C) with abundances 98.892%, 1.108%, and ~0%, respectively, giving an average atomic mass of 12.011 u.

ByteNotes

Short Answer

Medium difficulty • Direct answer format

Medium

Question 12

Quick Recall

Define molarity and molality. Which one is temperature-independent and why?

Molarity (M) is the number of moles of solute present in 1 litre of solution; molality (m) is the number of moles of solute present in 1 kg of solvent.
Molality is temperature-independent because it is expressed in terms of mass of solvent, which does not change with temperature.
Molarity is temperature-dependent because volume of a solution changes with temperature, altering the number of moles per litre.

ByteNotes

Short Answer

Easy difficulty • Direct answer format

Easy

Question 13

Quick Recall

How many SI base units are there? Name any four with their symbols.

The SI system has seven base units corresponding to seven fundamental scientific quantities, established by the 11th General Conference on Weights and Measures (CGPM) in 1960.
Four SI base units: metre (m) for length, kilogram (kg) for mass, second (s) for time, and kelvin (K) for thermodynamic temperature.
The remaining three are: ampere (A) for electric current, mole (mol) for amount of substance, and candela (cd) for luminous intensity.

ByteNotes

Premium Access

Unlock all Short Questions

You are viewing 13 free short questions from this chapter. Upgrade to Premium to unlock the remaining 12 questions.

Upgrade to Premium12 questions locked

Chapter sections

Chapter 1: Some Basic Concepts of Chemistry | Short Questions

What is matter? State the three physical states of matter.

Distinguish between a homogeneous and a heterogeneous mixture with one example each.

State the Law of Conservation of Mass and name its proposer.

Define atomic mass unit. What is 1 amu equal to in grams?

What is the mole? State the value of Avogadro's constant.

State Gay Lussac's Law of Gaseous Volumes with an example.

Define significant figures. How many significant figures are present in 0.0052 and 2.005?

Distinguish between precision and accuracy in measurement.

State the Law of Definite Proportions. Who proposed it?

What is dimensional analysis? Illustrate with one example.

What is average atomic mass? Why is it used instead of the mass of a single isotope?

Define molarity and molality. Which one is temperature-independent and why?

How many SI base units are there? Name any four with their symbols.

Unlock all Short Questions