Let's learn chemistry tutorial 2.0

Friday, September 1, 2023

acid base and salt pyq 2023

Part - A

acid base and salt - PYQ 2023

Few drops of aqueous solution of ammonium chloride are put on a universal indicator paper. The paper turns pink.
Study the following table and choose the correct option. [1 mark] [ CBSE 2023]
Two salts ‘X’ and ‘Y’ are dissolved in water separately. when phnolphthalein is added to these two solutions, the solutions ‘X’ turns pink and the solution ‘Y’ does not show any change in colour, therefore ‘X’ and ‘Y’ are
a. X is Na₂CO₃ and Y is NH₄Cl
b. X is Na₂SO₄ and Y is NaHCO₃
c. X is NH₄Cl and Y is Na₂SO₄
d. X is NaNO₃ and Y is Na₂SO₄ [1 mark] [CBSE 2023]
There are four solutions A, B, C and D with pH values as follows :-

Which solutions would liberate hydrogen gas with zinc ?
a. A only
b. D only
c. A and D only
d. B and c only [1 mark] [CBSE2023]
Assertion (A) : It is advised that while diluting an acid one should add water to acid and not acid to water keeping the solution continously stirred.
Reason (R) : The process of dissolving an acid into water is highly exothermic.
Answer the question selecting appropriate options given below :
a. Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of (A).
b. Both Assertion (A) and Reason (R) are true but Reason (R) is not the correct explanation of (A).
c. Assertion (A) is true, but Reason (R) is false.
d.Assertion (A) is false, but Reason (R) is true. [1 mark] [CBSE 2023]
A solution turns the colour of turmeric to reddish brown. if the same solution is poured on universal indicator, its colour would chhange to :
a. violet
b. blue
c. red
d. green [1 mark] [CBSE 2023]
If 10 ml of H₂SO₄ is mixed with 10 ml of Mg(OH)₂ of the same concentration, the resultant solution will give the following colour with universal indicator:
a. Red
b. yellow
c. Green
d. Blue [1 Mark] [CBSE 2020]
. A substance ‘X’ is used as a building material and is insoluble in water. when it reacts with dil. HCl, it produces a gas which turns lime water milky.
1. Write the chemical name and formula of ‘X’.
2. Write chemical equations for the chemical reactions involved in the above statements. [3 mark] [CBSE 2023]
A metal ‘M’ on reacting with dilute acid liberates a gas ‘G’. The same metal also liberates gas ‘G’ when reacts with a base.
1. Write the name of gas ‘G’.
2. How will you test the presence of this gas?
3. Write chemical equations for the reactions of the metal with (i) an acid and (ii) a base. [3 marks] [CBSE 2023]
1. what property do acids and bases have in common ? Explain it with an example.
2. A compound which is prepared from gypsum has the property of hardening when mixed with water.
  Identify the compound and write its formula. How is this compound prepared ? Describe it in the form of a chemical equation only. [3 mark] [CBSE 2023]
1. Write the chemical name and molecular formula of tooth enamel.
2. How does it get corroded ? What is the preventive measure for this ? [3 mark] [CBSE 2023]
A chemical compound ‘X’ is used in the soap and glass industry. It is prepared from brine.
1. Write the chemical name, common name and chemical formula of ‘X’.
2. Write the equation involved in its preparation.
3. What happens when it is treated with water containing Ca or Mg salts? [3 Marks] [CBSE 2020]
Write the chemical formula of washing soda. How can it be obtained from baking soda ? List two industries in which washing soda is used for other purposes than washing clothes. [3 Marks] [CBSE 2019]
State the effect of concentration of H⁺ (aq) ions on the nature of the solution. Do basic solutions also have H⁺ (aq) ions ? If yes, then why are these basic? [3 Marks] [CBSE 2019]
2 mL of sodium hydroxide is added to a few pieces of granulated zinc metal taken in a test tube. When the contents are warmed, a gas evolves which is bubbled through a soap solution before testing. Write the equation of the chemical reaction involved and the test to detect the gas. Name the gas which will be evolved when the same metal reacts with dilute solution of a strong acid. [3 Marks] [CBSE 2018]
The pH of salt used to make tasty and crispy pakoras is 14. Identify the salt and write a chemical equation for its formation. List its two uses. [3 Marks] [CBSE 2018]

Part - B

1 Mark:

1. How does the flow of acid rain water into a river make the survival of aquatic life in the river difficult? [CBSE, 2008]

2. What effect does an increases in concentration of 𝐻+(𝑎𝑞. ) in a solution have on the 𝑝𝐻 of solution?

[CBSE, 2009]

3. During summer season, a milkman usually adds a very small amount of baking soda to fresh milk. Give one reason.

[CBSE Sample Paper 2008]

4. Dry Hydrogen Chloride gas does not turn blue litmus red whereas Hydrochloric acid does. Give one reason.

[CBSE Sample Paper 2008]

2 Marks:

1. Write the chemical formula for washing soda. How may it be obtained from baking soda? Name an industrial use of

washing soda other than washing clothes.’

[CBSE, 2008]

2. I. Name the products formed when sodium hydrogen carbonate is heated.

II. Write the chemical equation for the reaction involved in the above.’

[CBSE, 2009]

3 Marks:

1. Baking soda is used in small amount in making bread and cake. It helps to make these soft and spongy. An aqueous

solution of baking soda turns red litmus blue. It is also used in soda acid fire extinguisher.

Use this information to answer the following questions:

I. How does Baking Soda help to make cakes and bread soft and spongy?

II. How does it help in extinguishing fire?

III. is the 𝑝𝐻 value of baking soda solution lesser than or greater than 7?

[CBSE Sample Paper 2008]

2. Answer the following:

[CBSE Sample Paper 2008]

a) Why is Plaster of Paris written as 𝐶𝑎𝑆𝑂4 ⋅ ½ 𝐻2𝑂? How is it possible to have half a water molecule attached to

𝐶𝑎𝑆𝑂4?

b) Why is Sodium Hydrogen Carbonate an essential ingradiant in antacids.?

c) When electricity is passed through an acquous solution of sodium chloride, three products are obtained. Why is

the process called chlor-alkali?

3. “𝑝𝐻 has a great importance in our daily life” explain by giving three examples.

A compound which is prepared from gypsum has the property of hardening when mixed with a proper quantity of

water. Identify the compound and write its chemical formula. Write the chemical equation for its preparation. Mention

any one use of the compound.

Part - C

Bleaching powder is soluble in cold water giving a

milky solution due to-

(a) available chlorine

(b) lime present in it

(d) The absorption of carbon dioxide from atmosphere

Ans : (b) lime present in it

Bleaching powder is actually a mixture of calcium

hypochlorite CaOCl2 and the basic chloride CaCl2

with some slaked, Ca OH ( )

2 .

21. Reaction of an acid with a base is known as-

(a) decomposition (b) combination

Ans : (d) neutralization

In a neutralization reaction an acid reacts with a base

and forms salt and water.

22. Which of the following acid does not react with metals-

(a) sulphuric acid (b) phosphoric acid

Ans : (c) carbonic acid

23. Bleaching powder gives smell of chlorine because it-

(a) is unstable

(b) gives chlorine on exposure to atmosphere

(d) contains excess of chlorine

Ans : (b) gives chlorine on exposure to atmosphere

Sunday, August 6, 2023

Assignment icse chemistry class 9th

Prepared by Akhilesh tiwari

SECTION - 1

Balance the following equations :
1. CaCO₃ (s) +HCl (aq) → CaCl₂ (aq) + H₂O (l) + CO₂(g)
2. Zn (S) + HCl (aq) → ZnCl₂ (aq) + H₂ (g)
3. MnO₂ (s) + HCl (aq) → MnCl₂(aq) + H₂O (l) + Cl₂ (g)
4. Na₂CO₃ (s) + H₂SO₄ (aq) → Na₂SO₄(aq) + H₂O (l) + CO₂ (g)
5. Mg₃N₂(s) + H₂O (l) → Mg(OH)₂ (s) + NH₃(g)
6. NH₃ (g) + O₂ (g) → N₂ (g) + H₂O (l)
7. MgCl₂ (aq) + Na₂CO₃ (aq) → MgCO₃ (aq) + NaCl (aq)
8. Pb3O4àPbO + O2
9. P + HNO3à NO2 + H2O + H3PO4
10. NO2 + H2O à HNO2 + HNO3
11. PbO + NH3àPb + H2O + N2
Write the formulae and balance the following equation :
1. Zinc + dil. Sulphuric acid → Zinc sulphate + hydrogen.
2. Ammonium sulphate + calcium hydroxide → Calcium sulphate + ammonia + water.
3. Lead dioxide + hydrochloric acid → Lead chloride + water + chlorine.
4. Aluminum oxide + sulphuric acid → Aluminum sulphate + water.
5. Iron + conc. Sulphuric acid → Iron sulphate + sulphur dioxide gas + water.
What is the valency of :
1. Fluorine in CaF₂
2. Sulphur in SF₆
3. Phosphorous in PH₃
4. Carbon in CH₄
5. Nitrogen in the following compounds : N₂O₃ , N₂O₅ , NO₂ , NO.

SECTION - 2

What are the limitations of chemical equation ?
MNO₃ is a formula of a nitrate of a metal M. write down the formulae of :
- Oxide of M
- Nitride of M
- Sulphate of M
1. Explain the term ‘valency’ and ‘variable valency’.
2. How are the elements with variable valiancy named ?
What do you understand by the term chemical formula ? What information is given by the formula NH3 ?
Define balanced and unbalanced equation .
Give the names of the following compounds :
Cu2O, CuO , Hg2O, HgO, FeO, Fe2O3
What are the information conveyed by a chemical equation?

Saturday, July 15, 2023

Atomic structure|| class 11th

prepared by AKHILESH TIWARI

UNIT 2 STRUCTURE OF ATOM

According to Dalton theory of atom(1808) -

All matter is composed of extremely small particles called atoms.
· The atom consists of smaller particles such as electron, proton and neutron.
· These particles are regarded as fundamental particles.
· Dalton theory explained the laws of chemical combination

· Dalton couldn’t explain the charge produced by rubbing ebonite

with silk or fur.

DISCOVERY OF ELECTRONS

The electrons were discovered by conducting an experiment by using a simple apparatus known as Cathode rays Discharge tube tube or Crookes tube.

· It consists of a sealed glass tube of about 50 cm lengths.
· Two metal electrodes are fused to the ends.
· A side tube is connected to a vacuum pump.
· The discharge tube is filled with a gas under study.
· The two electrodes are connected to a source of high voltage (1000 V) And very low pressure .
· Croockes said that at very low pressure, air being conductor of electricity.

OBSERVATIONS and properties :

· When the discharge tube containing the gas is at 1 atm pressure and at high voltage, the gas remains non conducting.
· When the pressure of the gas inside the tube is less than 1 mm of mercury, a dark space appears near the cathode. This is known as Crookes dark space.
· When the pressure is reduced to 0.01 mm Hg, it fills the entire tube.
· When the pressure is further reduced to 10^-4 mm Hg, the electric discharge passes between the electrodes wall of the tube coated with ZnS (fluorescent screen) begins to glow.
·


	This is due to the striking of some invisible rays from the cathode.

· These rays which start from the cathode and move towards the perforated anode, so called cathode rays.
• They move in straight lines.
• These rays are called cathode rays or cathode ray particles.
• These rays deflect towards anode. These rays consist of negatively charged material particles called electrons.
• Properties of cathode rays don’t depend upon cathode material or gass filled in discharge tube.
• Cathode rays produce mechanical effects.
• It indicates that cathode rays themselves are negatively charged.
• When a magnetic field is applied perpendicular to the path of cathode rays, they get deflected in the direction expected for negative particles. This direction of deflection shows that cathode rays are –vely charged.
When cathode rays are allowed to strike a thin metal foil, it gets heated up.
Cathode rays produce, x-rays when they strike heavy metals like tungsten, copper etc.
Cathode rays produce fluorescence on glass walls, ZnS etc.
Cathode rays penetrate through thin metallic foils.
Cathode rays affect photographic plates.

DETERMINATION OF CHARGE TO MASS RATIO (e/m) OF ELECTRONS

In 1897 J.J. Thomson determined the e/m of the electron.
He measured the deflection of cathode rays under the simultaneous influence of electric and magnetic fields.
A narrow beam of cathode rays is generated by electric discharge in a gas at low pressure.
If an electric field is applied at right angles to the beam, the beam having negative charge is attracted to the positive plate of the field.
the beam thus travels a parabolic path and strikes at another point on the screen.
A magnetic field is now applied to the beam in a direction at right angles to that of the electric field.
The beam undergoes deflection in the opposite direction.
Deflection ∝ strenght of magnetic feild and electric field.

Deflection ∝ magnitude of negative charge.

Deflection ∝ 1/ mass of particles.

The strength of the two fields are so adjusted that the beam strikes the screen at the original position.
Lighters the particle greater the deflection in the field.
As voltage of electric field and strength of magnetic field increase deviation from orginal pathway increases .

e – charge of electron

Me – mass of electron

Charge on the electron

The charge of an electron was determined by Robert Millikan in 1909 by oil drop

experiment.

· In this method, a spray of oil droplets is produced by an atomizer.
· The oil droplets enter the apparatus through a small hole.
· It allowed to fall in between two charged plates.
The motion of the droplets is observed with a telescope.
· The space between the charged plates is irradiated with x-rays.
· The x-rays ionize the molecules of the air.
· One or more electrons produced may be absorbed by an oil droplet.
· The oil droplet as a result becomes negatively charged.
· By measuring the velocity of a given oil droplet as it falls freely under the influence of gravity and then in an electric field, it is possible to calculate the charge on the droplet. Q= n e
· This charge is considered to be electronic charge.
· The charge on the electron is found to be - 1.602 x 10⁻¹⁹ coulombs.