#### Basic Concepts of Chemistry and Chemical Calculations - Important Question Paper

11th Standard

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Chemistry

Time : 01:00:00 Hrs
Total Marks : 50

Part A

15 x 1 = 15
1. What is the mass of precipitate formed when 50 ml of 8.5 % solution of AgNO3 is mixed with 100 ml of 1.865 % potassium chloride solution?

(a)

3.59g

(b)

7g

(c)

14 g

(d)

28 g

2. Which among the following statement(s) describe an element?
i) It is a pure substance which could be split into two or more simpler substance.
ii) It is a pure substance which cannot be split into simpler substance
iii) It's composition is not uniform
iv) All the above

(a)

only (iv)

(b)

only (ii)

(c)

(ii) and (iii)

(d)

(i) and (iii)

3. How many moles of magnesium phosphate Mg3(PO4)2 Will Contain 0.25 moles of oxygen atoms?

(a)

0.02

(b)

3.125 x 10-2

(c)

1.25 x 10-2

(d)

2.5 x 10-2

4. Assertion: Equal volumes of all the gases do not contain equal number of atoms
Reason: Atom is the smallest particle which takes part in chemical reactions.

(a)

Both assertion and reason are correct and reason is the correct explantion for assertion

(b)

Both assertion and reason are correct but reason  is not the correct explantion for assertion

(c)

Assertion is true but reason are false

(d)

Both assertion and reason are false

5. Two elements X and Y ( atomic mass of X = 75; Y = 16) combine to give a compound having 76% of X. The formula of the compound is?

(a)

XY

(b)

X2Y

(c)

X2Y2

(d)

X2Y3

6. The percentage yield of reaction can be described as the.................................times 100%.

(a)

amount of product you could make if the reaction went to completion

(b)

total of materials involved in a reaction

(c)

amount of desired product divided by the amount of unwanted product

(d)

amount of product obtained divided by the maximum possible amount of product

7. How many significant figures should be used for the answer to the following calculation?

$\frac { (0.82056)\ (298.15)\ (0.379) }{ (0.9480) }$

(a)

2

(b)

3

(c)

4

(d)

5

8. In the reaction, 4NH3(Xg) + 5O2(g) $\rightarrow$ 4NO(g)+6H2O(I) when 1 mole of ammonia and mol of O2 are made to reactent completion then

(a)

1.0 mol of H2O is produced

(b)

1.0 mol of NO will be produced

(c)

all the oxygen will be consumed

(d)

all the ammonia will be consumed

9. In the reaction of sodium thiosulphate with I2 in aqueous medium, the equivalent weight of dodium thisulphate is equal to

(a)

molar mass of sodium thiosulphate

(b)

the average of molar masses of Na2S2O3 and I2

(c)

half the molar mass of sodium  thiosulphate

(d)

molar mass of sodium thiosulphate x 2.

10. The number of moles of H2 in 0.224 L of hydrogen gas at STP (273 K, 1 atm) is

(a)

0.1

(b)

0.01

(c)

0.001

(d)

1

11. The molarity of water given its density is 1000 kg m-3  is

(a)

11.11M

(b)

18.00M

(c)

36.00M

(d)

55.55M

12. The number of molecules in 16g of methane is:

(a)

3.023 x 1023

(b)

6.023 x 1023

(c)

16/6.023 x 1023

(d)

6.023/3 x 1023

13. How many equivalents of sodium sulphate is formed when sulphuric acid is completely neutralized by a base NaOH:

(a)

0.2

(b)

2

(c)

0.1

(d)

1

14. How many molecules of hydrogen is required to produce 4 moles of ammonia?

(a)

15 moles

(b)

20 moles

(c)

6 moles

(d)

4 moles

15. The number of moles of H, in 2.24 litre of hydrogen gas at STP is _______________

(a)

1

(b)

0.1

(c)

0.01

(d)

0.001

16. Part B

5 x 2 = 10
17. The density of carbon dioxide is equal to 1.965 kgm-3 at 273 K and 1 atm pressure. calculate the molar mass of CO2

18. What is the empirical formula of the following?
i) Fructose (C6 H12O6) Found in honey
ii) Caffeine  (C8H10N4 O2) a substance found in tea and Coffee

19. Balance the following equations by ion electron method -
i) ${ KMn }O_{ 4 }+{ SnCl }_{ 2 }+HCI\longrightarrow MnCI_{ 2 }+{ SnCI }_{ 4 }+{ H }_{ 2 }O+KCI$
ii) ${ C }_{ 2 }{ O }_{ 4 }^{ 2- }+{ Cr }_{ 2 }{ O }_{ 7 }^{ 2- }\longrightarrow { Cr }^{ 3+ }+{ CO }_{ 2 }$ (in acid medium)
iii) ${ Na }_{ 2 }{ S }_{ 2 }{ O }_{ 3 }+{ I }_{ 2 }\longrightarrow { Na }_{ 2 }{ S }_{ 4 }{ O }_{ 6 }+NaI$
iv) $Zn+{ NO }_{ 3 }^{ - }\longrightarrow { Zn }^{ 2+ }+No$

20. Calculate the equivalent masses of the following - HNO3

21. What is meant by Plasma state? Give an example.

22. Part C

5 x 3 = 15
23. Calculate the mass of the following: 1 atom of silver

24. How much mass (in gram units) is represented by the following?
0.2 mol of NH3

25. Calculate the oxidation number of underlined atoms of the following:
NO3-

26. Calculate the number of moles present in the following 120g of sodium hydroxide

27. Define the following: (i) Element, (ii) Compound.

28. Part D

2 x 5 = 10
29. Balance the following equations by oxidation number method.
K2Cr2O7 + HI ⟶ KI + Crl3 + H2O + I2

30. ${ 2NH }_{ 3 }\left( g \right) +{ CO }_{ 2 }\left( g \right) \rightarrow \underset{Urea}{H_2N}-\overset { \underset { || }{ O } }{ C } -{ NH }_{ 2 }\left( aq \right) +{ H }_{ 2 }O(I)$
(i) If the entire quantity of all the reactants is not consumed in the reaction which is the limiting reagent?
(ii) Calculate the quantity of urea formed and unreacted quantity of the excess reagent. The balanced equation is
$\overset { { 2NH }_{ 3 }+{ CO }_{ 2 } }{ \underset { { H }_{ 2 }NCON{ H }_{ 2 }+{ H }_{ 2 }O }{ \downarrow } }$