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(a) Since vinegar is acetic acid so it can’t be used to treat bee sting because bee injects acid into the skin.

(b) Since baking soda is basic in nature so it can’t be used to treat wasp sting because wasp injects alkaline liquid into the skin.

(a) Common salt contains impurity of magnesium chloride (MgCl₂) which is of deliquescent nature. When exposed to atmosphere, it becomes moist. Therefore common salt becomes sticky during the rainy season. 

(b) Blue vitriol (CuSO₄ 5H₂O) during heating changes to a anhydrous copper sulphate (CuSO₄) which is white in colour.

Take some water in a test tube and add concentrated H₂SO₄ to it. Shake the test tube well. If you touch the bottom of the test tube,

When potassium nitrate (KNO₃) crystals are heated with concentrated sulphuric acid (H₂SO₄) then vapours of nitric acid (HNO₃) are evolved and potassium bisulphate is also formed. 

KNO₃ + H₂SO₄→ HNO₃ + KHSO₄

False 

The process should be that acid must be added slowly to water with constant stirring. If water is added slowly to the acid with constant stirring then due to the exothermic reaction going on the acid might splash away from the beaker causing burns.

Work done = Kinetic Energy possessed by a body. 

Kinetic Energy = \(\frac{mv^2}{2}\)

Given 

Mass (m) = 80 Kg; 

Velocity (v) = 10 m/s;

Kinetic Energy = \(\frac{80\times10^2}{2}\)

⇒ Kinetic Energy = \(\frac{8000}{2}\) = 4000 J

Hence the work done is 4000 J.

(a) The chemical present in the sting must be base because vinegar (aceticacid) is used to heal or neutralize the effect of wasp stings. 

(b) Since bee stings are treated by backing soda which is a base it means they must contain some acid. If baking soda is not available in the house, solution of ammonium hydroxide NH₄OH can be used for the same purpose. 

No, tartaric acid does not evolve any carbon dioxide during baking. Its role is to react with Na₂CO₃ formed when NaHCO₃ decomposes.

Two characteristics of acids:-

i. Acids are sour in taste. 

ii. They produce H⁺ ions upon dilution. 

Two characteristics of bases:-

i. Bases are bitter in taste.

ii. They produce OH^- ions upon dilution.

(a). Water should not be added to concentrated acid because the process of dissolving an acid or a base in water is a highly exothermic one. If water is added to an acid then the heat generated may cause the acid to splash out and cause burns.

(b). Pain or irritation is caused in our stomach when there is production of an excess amount of acid in our body. Antacids are basic in nature. Hence antacids are required when there is pain or irritation in the stomach to neutralize the effect of the excess acid.

(c). Bee-stung injects acid in our body. Baking soda is a base. Hence, baking soda should be rubbed on bee-stung area to neutralize the effect of the acid.

Tooth enamel is made up of compound calcium phosphate. Its pH is 5.5.

Bacteria present in the mouth works on the leftover food particles and produce acid. Tooth pastes are used for neutralising the excess acid.

• Sodium hydroxide (NaOH) is a commonly used base and is hygroscopic, that is, it absorbs moisture from the atmosphere and becomes sticky. 
• The acidic oxides react with base to give salt and water. 
• The reaction between NaOH and CO₂ can be given as 

2NaOH + CO₂ → Na₂CO3 + H₂O

The production of sodium hydroxide and chlorine from brine solution by through electricity is known as chlor-alkali process. 

When electricity is passed through a highly concentrated solution of salt and water (Brine solution), the electrolysis of water takes place and we obtain three different products. We get chlorine gas on anode and hydrogen gas and sodium hydroxide solution on cathode.

When electricity is passed through an aqueous solution of sodium chloride, it decomposes to form sodium hydroxide. This process is called chlor-alkali process.

It is called so because the products formed in the reaction are chlorine and sodium hydroxide. Here chlor stands for chlorine and alkali is for sodium hydroxide.

Sodium hydroxide (NaOH) is a commonly used base and is hygroscopic, i.e., lt absorbs moisture from the atmosphere and becomes sticky. 

The acidic oxides react with base to give salt and water.

2NaOH(aq) + CO₂(g)→Na₂CO₃(aq) + H₂O(l)

X-NaOH (Sodium hydroxide)

When electricity is passed through an aqueous solution of sodium chloride, it decomposes to from sodium hydroxide.

2NaCl+2H₂O → 2NaOH+Cl₂+H₂

Neutralisation reaction

NaOH+ HCl → NaCl+H₂O

Uses of washing soda (Na₂CO₃.10H₂O):

1) Washing soda (sodium carbonate) is used in glass, soap and paper industries. 

2) It is used in the manufacture of sodium compounds such as borax. 

3) Sodium carbonate can be used as a cleaning agent for domestic purposes. 

4) It is used for removing permanent hardness of water.

Uses of baking soda (NaHCO₃ 10H₂O) : 1) 

1) Baking soda (Sodium hydrogen carbonate) is used for faster cooking. 

2) Baking powder (a mixture of baking soda and a mild acid) is used in preparation of cakes. 

3) Sodium hydrogen carbonate is also an ingredient in antacids. 

4) It is also used in soda – acid, fire extinguishers. 

5) It acts as a mild antiseptic.

1. (i) Electrolysis

2. (ii) Bleaching powder

3. (ii) \(CaOCl_2\)

4. (i) Chlorine gas

5. (ii) Bleaching powder

1. (iii) All of the above

2. (iii) All of the above

3. (ii) Sodium carbonate

4. (i) Washing soda

5. (iv) Both A and B

(a) Atom: 

i. The building blocks of all matter are atoms. Atoms are very small. 

ii. They are smaller than anything we can imagine or compare with. 

(b) Molecule: 

i. A molecule is general a group of two or more atoms that are chemically bonded together. They are tightly held together by attractive forces. 

ii. A molecule can be defined as the smallest particles of an element or a compound that is capable of an independent existence. 

iii. A molecule shows all the properties of a particular substance. 

iv. Atoms of the same element or different element join together to form molecules. 

(c) Avogadro’s number: 

i. Avogadro’s number is the number of particles (atoms, ions or ions) present in one mole of any substance is fixed with a value of 6.022 × 10²³ . 

ii. This is an experimentally obtained value. 

(d) Valency: 

i. The combining power or capacity of an element is known as valency. 

ii. Valency can be used to ind out how the atoms of an element will combine with the atoms of another element to form a chemical compound.

(e) Molar mass: Molar mass is the mass of one mole of any substance. One mole of any species (atoms, molecules, ions or particles) is that quantity in number having a mass equal to its atomic or molecules mass in grams. Molar mass is represented by “M”

Number of moles(n) = \(\frac{Given\,mass(m)}{Molar\,mass(M)}\)

We can write, 

Molar mass (M) = mass (m) × Number of moles(n).

• The chemical formula of baking powder is sodium hydrogencarbonate (NaHCO₃).
• Whereas, that of washing soda is sodium carbonate (Na₂CO₃.10H₂O) Sodium hydrogencarbonate on heating gives CO₂ gas which will turn lime water milky whereas no such gas is obtained from sodium carbonate.

\(2NaHCO_3 \overset{Heat}\rightarrow Na_2CO_3+H_2O+CO_2\)

\(Na_2CO_3.10H_2O \overset{Heat}\rightarrow Na_2CO_3+10H_2O\)

(a) Baking soda is sodium hydrogencarbonate. 

On heating, it is converted into sodium carbonate which is bitter to taste 

\(2NaHCO_3\overset{Heat}\rightarrow Na_2CO_3 + H_2O + CO_2\)

(b) Baking soda can be converted into baking powder by the addition of appropriate amount of tartaric acid to it. 

(c) The role of tartaric acid is to neutralise sodium carbonate and cake will not taste bitter

1. (i) Baking soda

2. (i) Baking soda

3. (ii) Sodium chloride

4. (ii) Sodium bicarbonate

5. (ii) FALSE

(a). While making baking powder tartaric acid id being added to it because when this mixture is heated or mixed with water carbon dioxide gas is evolved which causes the bread or cake to rise making them spongy and soft. 

(b). Bleaching powder is used for disinfecting drinking water because bleaching powder is an oxidizing agent and helps in removing or killing the germs.

(c). Strong acid means those acids which gives a very high H⁺ ion concentration upon dilution or those which are able to generate a greater volume of H⁺ ions per unit quantity whereas concentrated acid means how many moles of the acid is present in a given quantity of a solvent. Higher concentration means greater amount of the acid per unit of the solvent.

Plaster of Paris is different from Gypsum in term of water of crystallization.Gypsom has 2 mole of water of crystallization where as Plaster of Paris has half mole of water of crystallization.Plaster of Paris is prepared from heating gypsum.

CaSO₄.2H₂O ------Heat/273 k--> CaSO₄.1/2 H₂O

When plaster of Paris is mixed with water it get converted into Gypsum

CaSO₄.1/2 H₂O + 3/2 H₂O ----------> CaSO₄.2H₂O

The use of plaster of Paris are- 

(i) It is used for making moulds or casts for toys pottery, ceramics etc. 

(ii) In surgical bandages for setting fractured bones.

a) Formula of sulphuric acid is H₂SO₄. 

Molecular mass of H₂SO₄ = 2 × 1 + 1 × 32 + 4 × 16 = 2 + 32 + 64 = 98 u 

∴ Molar mass of H₂SO₄ = 98 g 

b) Formula of glucose is C₆H₁₂O₆. 

Molecular mass of C₆H₁₂O₆ = (6 × 12) + (12 × 1) + (6 × 16) = 72 + 12 + 96 = 180 u 

∴ Molar mass of C₆H₁₂O₆ = 180 g.

The formula of Gypsum is: CaSO₄.2H₂O and plaster of Paris having formula CaSO₄.1/2 H₂O is obtained upon heating gypsum.

a) Molecular mass : 

The molecular mass of a substance is the sum of the atomic masses of all the atoms in a molecule of a substance. 

b) Formula unit mass : 

The formula unit mass of a substance is a sum of the atomic masses of all atoms in a formula unit of a compound.

c) Mole : 

1) One mole of a substance is the amount of the substance which contains as many particles or entities that are equal to the atoms present in exactly 12 grams of C¹² isotope. 

2) The number of particles present in one mole of any substance has a fixed value of 6.022 × 10²³. This number is called Avogadro’s constant (N_A).

d) Molar mass : 

The mass of 1 mole of a substance which is expressed in grams is called its molar mass.

Calcium sulphate hemihydrate -CaSO₄.1/2H₂O

Calcium sulphate dihydrate - CaSO₄.2H₂O.

By mixing with water

CaSO₄.1/2H₂O+1 1/2H₂O  CaSO₄.2H₂O

Phenolphthalein and Methyl Orange: The synthetic (chemical) indicators to find the presence of acids and bases.

We know, 1 mole = 6.022 × 10²³ 

Now, to calculate mass, apply the formula:

Number of moles(n) = \(\frac{Mass(m)}{Molar\,mass(M)}\)

we can write:

Mass(m) = Number of moles (n) × Molar mass of N₂ (M) 

Mass = 1 mol × 28g/mol Mass = 28g 

Thus, the mass of 6.022 × 10²³ atoms of nitrogen is 28g

A) Mass spectrometer

When NaHCO₃ is heated or mixed with water a reaction takes place which leads to the evolution of carbon dioxide gas. Now carbon dioxide extinguishes ire very well hence, it is used in soda-acid ire extinguisher and also the carbon dioxide produced during the reaction causes the bread or cake to rise making them soft and spongy. Hence, NaHCO₃ is used for making baking powder.

A) 6.022 × 10²³ 

D) any one of the above

Given: 

Number of moles = 7 

Atomic mass of H₂SO₄ = 2 ×1 + 32 + 4 × 16 = 98g/mol 

To find out the mass of sulphuric acid, apply the formula given: 

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

⇒ 7 =\(\frac{mass}{98\,g/mol}\)

⇒ Mass = 7 mol × 98g/mol

⇒ Mass = 686g 

Thus, the mass of sulphuric acid is 686g.

This means that a molecule of oxygen is 32 times heavier than 1/12 of a Carbon-12 atom.

Correct option is D) Wolfram

Avogadro constant: The number of particles present in one mole of any substance is the Avogadro constant (NA). This is equal to 6.022 × 10²³ .

The number of particles present in one mole of any substance is the Avogadro number (N_A). 

This is equal to 6.022 × 10²³.

C) 6.02 × 10²² 

D) 6.022 × 10²³

The mass of 1 mole of a substance which is expressed in grams is called its molar mass.

The formulae of Gypsum is CaSO₄. 2H₂O and Plaster of Paris is CaSO₄. 1/2H₂O.

1. Gypsum plaster (or) Plaster of Paris (POP) is produced by heating gypsum to about 300°F.

2. A large gypsum deposit is found at Montmartre in Paris (France). 

3. This gave the name Plaster of Paris to calcium sulphate hemihydrates. 

4. The term plaster can refer to gypsum.

Calcium sulphate hemihydrates are used as plaster for supporting fractured bones in the right position. So, it is called Plaster of Paris.

A) 6.022 × 10²³ 

True

A mole always represents for gases, 22.4 litres of volume at 0°C and 1 atmospheric pressure which is known as standard temperature and pressure (STP).

The given statement is correct.