Q34 of 36 Page 1

Match the following pH values 1, 7, 10, 13 to the solutions given below:

• Milk of magnesia


• Gastric juices


• Brine


• Aqueous Sodium hydroxide.


Amit and Rita decided to bake a cake and added baking soda to the cake batter


Explain with a balanced reaction, the role of the baking soda. Mention any other use of baking soda.


OR


(i) Four samples A, B, C and D change the colour of pH paper or solution to Green, Reddish-pink, Blue and Orange. Their pH was recorded as 7, 2, 10.5 & 6 respectively. Which of the samples has the highest amount of Hydrogen ion concentration? Arrange the four samples in the decreasing order of their pH.


(ii) Rahul found that the Plaster of Paris, which he stored in a container, has become very hard and lost its binding nature. What is the reason for this? Also, write a chemical equation to represent the reaction taking place.


(iii) Give any one use of Plaster of Paris other than for plastering or smoothening of walls.


 Solution pH


 Milk of magnesia 10 (basic)


 Gastric juices 1 (most acidic)


 Brine 7 (neutral)


 Aqueous Sodium hydroxide 13(most basic)


Baking soda is represented by NaHCO3 undergoes thermal decomposition to form Na2CO3, CO2 and H2O; CO2 makes the cake fluffy & soft.It is represented by the following reaction:


NaHCO3→ Na2CO3 + CO2 + H2O


Uses


1. It is used for preparing baking powder and effervescent drinks. 2. It is used as an antacid. It corrects acidity in the stomach.


3. It is used in soda-acid type fire extinguishers.


OR


(i) a) B


b) C>A>D>B


(ii) Plaster of paris gets converted into hardened mass (Gypsum) due to presence of moisture in the atmosphere.


CaSO4+1 1/2 H2O→ CaSO4.2H2O


(iii) Making toys/dolls or statues /fixing broken limbs/making decorative materials.


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a. Explain the formation of Calcium Chloride with the help of electron dot structure. (At numbers: Ca = 20; Cl = 17)

b. Why do ionic compounds not conduct electricity in solid state but conduct electricity in molten and aqueous state?


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Refractive index of water with respect to air is 1.33 and that of diamond is 2.42.

(i) In which medium does the light move faster, water or diamond?


(ii) What is the refractive index of diamond with respect to water?


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Trace the changes that take place in a flower from gamete formation to fruit formation.

 36

In the given circuit, A, B, C and D are four lamps connected with a battery of 60V.


Analyse the circuit to answer the following questions.


(i) What kind of combination are the lamps arranged in (series or parallel)?


(ii) Explain with reference to your above answer, what are the advantages (any two) of this combination of lamps?


(iii) Explain with proper calculations which lamp glows the brightest?


(iv) Find out the total resistance of the circuit.


OR


PQ is a current carrying conductor in the plane of the paper as shown in the figure below.



(i) Find the directions of the magnetic fields produced by it at points R and S?


(ii) Given r1> r2, where will the strength of the magnetic field be larger? Give reasons.


(iii) If the polarity of the battery connected to the wire is reversed, how would the direction of the magnetic field be changed?


(iv) Explain the rule that is used to find the direction of the magnetic field for a straight current carrying conductor.