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Significant figures are meaningful digits which are known with certainty. The uncertainty is indicated by writing the certain digits and the last uncertain digit.

It is defined as the standard of reference chosen to measure a physical quantity.

Molecules consist of different atoms or same atoms. e.g. molecule of hydrogen contains two atoms of hydrogen where as molecule of water contain two atoms of hydrogen and one of oxygen.

Compound is formed when two or more than two different atoms e.g. water carbondioxide, sugar etc.

Two or more atoms of same elements combine to form molecule.

e.g.O₂, N₂, Cl₂, etc.

Two or more atoms of different elements combine to form compound

e.g. H₂O, NH₃, CO₂ etc.

The two different systems of measurement are the English System and the Metric Systems.

Accuracy is the agreement of a particular value to the true value of the result.

The ability of the eye lens to adjust its focal length is called accommodation.

(i) 1 mol of Ar = 6.022×10²³atoms 

∴ 52 mol of Ar = 52×6.022×10²³atoms = 3.131×10²⁵atoms 

(ii) 1 atom of He = 4 u of He 4 u of He = 1 Atom of He 

∴ 52 u of He = (1/4) × 52 = 13 atoms 

(iii) 1 mol of He = 4 g = 6.022×10²³atoms 

∴ 52 g of He = (6.022×10²³/4) × 52 atoms 

= 7.8286×10²⁴atoms

Here—OH group is predominant and the alcohol molecules can form hydrogen bonds with water molecules.

• Looking glass

• Used in submarines

• Solar cooker 

• Kaleidoscope

SI unit of molarity is mole/liter.

The SI units of molarity is mol dm^-3

It is due to the greater steric repulsions between bulky R(alkyl) groups.

CaCO₃(s) + 2HCl(aq) → CaCl₂(aq) + CO₂ (g) + H₂O(l)

Number of moles of HCl = Volume in liters × Molarity

= \(\frac{250}{1000}\) x 0.76 = 0.19 mol.

Mass of CaCO₃ = 1000 g

Number of moles of CaCO₃

= \(\frac{Mass}{Molar\,mass}\) = \(\frac{1000\,g}{100\,g\,mol^{-1}}\)

1 mole of CaCO₃ reacts with 2 moles of HCI

10 moles of CaCO₃ will react with 2 × 10 = 20 moles of HCl

But, we have only 0.19 mol of HCl, therefore,

HCl is the limiting reactant.

2 moles of HCI give 1 mole of CaCl₂

0.19 mole of HCl will give = \(\frac{1}{2}\) x 0.19

= 0.095 moles of CaCl₂.

(i) 2(ii) 3(iii) 4(iv) 3(v) 4(vi) 5

CaCO₃ (s) + 2HCl (aq) → CaCl₂ (aq) + CO₂ (g) + H₂O (l)

1 mol                     2 mol

(40 + 12 + 48) g   2(1 + 35.5) g

= 100 g                 = 73 g

Amount of HCl in 25 mL of 0.75 M HCl

= M x V = 0.75 mpl L^-1 x 25 mL

= 0.75 mol L^-1 x 25/1000 L = {0.75 x 25}/{1000} mol

= 0.0188 mol

2 mol of HCl reacts with 100 g CaCO₃

0.0188 mol of HCl reacts with = {100 g x 0.0188}/{2} g CaCO₃

= 0.94 g CaCO₃

Distance covered = Speed×Time 

= 3.0 × 10⁸ms^-1 × 2.00 ns

= 3.0×10⁸ms^-1×2.00 ns×10^-9s/1ns 

= 6.00×10^-1m = 0.600m

Correct answer is 1.84 g, 43%

Fundamental rights are to be protected. The Constitution proposes remedial measures if the Fundamental Rights are violated. This is known as the Right to constitutional remedies. As per this right, if the Fundamental Rights are violated an individual can approach either the Supreme Court or the High Courts for enforcing them. The orders issued by the respective courts for the enforcement of the Fundamental rights are known as writs. Thus the right to constitutional remedies plays significant role in protecting our rights.

Speed of light = 3.0 x 10⁸ ms^-1

Time = 2.00 ns = 2 x 10^-9 s

Distance travelled by light in 1 second

= 3.0 x 10⁸ m

Distance travelled by light in 2 x 10^-9 s

= 3.0 x 10⁸ x 2 x 10^-9 = 6 x 10^-1 m

= 6.00 x 10^-1 m = 0.600 m

Mass of 6.022x10²³ atoms of Ag = 108 g 

Mass of one atom of Silver 108/ 6.022X10²³ = 1.79x10^-22g

Fundamental rights are those rights which cannot be denied to a person at any cost. Right to equality, right to freedom, right against exploitation, right to freedom of religion, cultural and educational rights and right to constitutional remedies are the fundamental rights.

Every individual wishes to lead a dignified life. This is not an easy task. When one gets freedom, equality and relief from exploitation, a dignified in made possible. The constitution provides all these rights to an individual through provision of fundamental rights. Thus it can be seen that fundamental rights are very essential for leading a dignified life.

1. Untouchability Offences Act 1955

2. Equality before law

3. Abolition of Titles

4. Equality of opportunity in public employment

5. Prohibition of discrimination on the basis of caste, religion, race sex play of birth.

6.022x10²³ molecules of iodine = 1 mol of iodine 

1.0x10²² molecules of iodine = 1/6.022X10²³ X1.0 X10²² 

= 0.0166 mol of iodine 

• Protection form child labour
• Protects citizens form forced labour
• Prohibits human trafficking
• Protects children and women from employment in factories and dangerous sectors

• Child labor
• Exploitation at job sites
• Forced labor
• Human trafficking
• Dangerous job conditions
• Slavery

(a) Used in torches, search lights and vehicle headlights. 

(b) Used as shaving mirror. 

(c) Used by dentist. 

(d) Used in solar furnance.

• Concave mirror 

• Convex mirror

(i) Concave mirror are used in torches, search-lights and vehicle headlights to get powerful parallel beams of light. 

(ii) They are also used as shaving mirrors to see a large image of the face. 

(iii) Dentists use concave mirrors to see large images of the teeth of patients. 

(iv) Large concave mirrors are used in making solar furnaces, solar cookers etc.

The ability of the eye to focus the distant objects as well as the nearby objects on the retina by changing the focal length of the eye lens is called power of accommodation.

The ideas included in the Right to equality are given below:

• Ensure equality before law
• Prohibition of discrimination on the basis of caste, religion, race, sex, place of birth, etc.
• Ensure equality of opportunity in public employment
• Abolition of titles

Given : 

Mass of acetic acid = 22 g 

To find : 

The number of moles and molecules of acetic acid 

Formulae : 

Number of moles = \(\frac{Mass\,of\,a\,substance}{Molar\,mass\,of\,a\,substance}\)

Number of molecules = Number of moles × Avogadro’s constant

Calculator : 

Mass of acetic acid = 22 g

Molecular mass of acetic acid,

CH₃COOH

= (2 × Average atomic mass of C) + (4 × Average atomic mass of H) + (2 × Average atomic mass of O)

= (2 × 12 u) + (4 × 1 u) + (2 × 16 u) 

= 60 u

∴ Molar mass of acetic acid = 60 g mol^-1

Number of moles = \(\frac{Mass\,of\,a\,substance}{Molar\,mass\,of\,a\,substance}\)

= \(\frac{22\,g}{60\,g\,mol^{-1}}\)

= 0.367 mol

Now, 

Number of molecules of acetic acid = Number of moles × Avogadro’s constant 

= 0.367 mol × 6.022 × 10²³ molecules/mol 

= 2.210 × 10²³ molecules

∴ Number of moles = 0.367 mol 

Number of molecules of acetic acid = 2.210 × 10²³ molecules.

Cultural and educational rights

• Used as reflectors in car headlights, searchlights, etc. 

• Used as shaving mirror. 

• Used in solar cooker to focus the sunlight on one point.

• Relative refractive index– It is the ratio of speed of light in one medium to the speed of light in another medium 

• Absolute refractive index– It is the ratio of light in vacuum to the speed of light in another medium.

• Freedom of speech and expression.
• Freedom to assemble peacefully, without arms. Besides these two rights, the following rights are also included in the right to freedom.
• Freedom to form associations.
• Freedom to travel anywhere in India.
• Freedom to reside anywhere in India
• Freedom to carry on any occupation, trade, or business
• Right to life and personal liberty.
• Right to free and compulsory education to all children in the age group of 6 -14 years.
• Protection from arbitrary arrest and detention.

• It is used as the rear view mirror in cars. 

• It is used in street lights as it diverge the light over larger area.

Answer is (ii) 27.27%

Indian Constitution ensures the right to freedom of religion. This enables people to believe in any religion. The right to freedom of religion ensures the right to protects, practice and propagate any religion. Freedom is also given to establish and maintain institutions for religious and charitable purposes. The country is not having any official religion. In this way the right to freedom of religion promotes secularism.

(iii) C₆H₁₂O₆

1. After adding sugar, potassium permanganate and glycerin to the dish, immediately step back because spark and solid potassium permanganate will be expelled from the dish. 

2. When potassium permanganate mixes with glycerin, a redox reaction starts. This reaction starts out really slow, but produces a lot of heat, so it will start to speed up bit by bit. As the potassium permanganate oxidises the sugar, it will speed up more and more until it finally starts to smoke and after that it will ignite.

The water heated by Akash will get heated in a shorter time because he kept his beaker near the hottest (non- luminous) zone of the flame. But Arul kept the beaker in the luminous zone which is moderately hot. So, it will take longer time.

A fuel is a very good source of heat. The heat energy produced by burning a fuel can be used directly to cook food, for running motor vehicles and factory machines, can be converted into electrical energy at thermal power stations. Wood and Petrol are examples of two common fuels.

(a) ignition temperature 

(b) air 

(c) water 

(d) kerosene 

(e) calorific value 

(f) flames 

(g) pollution

The water in the Ramesh's beaker will heat up in a shorter time. This is because the outermost zone of a flame is the hottest zone, while the yellow zone (in which Abida had kept the beaker) is less hot

Charge on oil drop = 6.39 x 10^-19 C

1.602 x 10^-19 C is the charge on 1 electron

∴ 6.39 x 10^-19 C will be charge on

= {6.39 x 10¹⁹}/{1.602 x 10^-19} = 4 electrons

Basicity of an acid is the number of replaceable hydrogen atoms present on a molecule of an acid is called basicity of an acid.