#### Basic Concepts of Chemistry and Chemical Calculations Important Questions

11th Standard

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Chemistry

Time : 01:00:00 Hrs
Total Marks : 50
5 x 1 = 5
1. An element X has the following isotopic Composition 200X = 90%, 199X = 8% and 202X = 2% The Weighted average atomic mass of the element X is closet to

(a)

201 u

(b)

202 u

(c)

199 u

(d)

200 u

2. When 6.3g of sodium bicarbonate is added to 30g of the acetic acid solution, the residual solution is found to weigh 33g. The number of moles of carbon dioxide released in the reaction is

(a)

3

(b)

0.75

(c)

0.075

(d)

0.3

3. Fe2 + $\longrightarrow$ Fe3+ + e- is a ________ reaction.

(a)

redox

(b)

reduction

(c)

oxidation

(d)

decomposition

4. 7.5 g of a gas occupies a volume of 5.6 litres at 0° C and 1 atm pressure. The gas is

(a)

NO

(b)

N2O

(c)

CO

(d)

CO2

5. Among the three metals, zinc, copper and silver, the electron releasing tendency decreases in the following order.

(a)

zinc >silver >copper

(b)

zinc >copper >silver

(c)

silver > copper >zinc

(d)

copper > silver > zinc

6. 5 x 2 = 10
7. What do you understand by the term mole

8. Distinguish between oxidation and reduction.

9. Give a brief account of classification of matter.

10. Calculate the equivalent masses of the following - HNO3

11. Calculate the oxidation number of underlined atoms of the following:
Na2[Fe(CN)6]

12. 5 x 3 = 15
13. Mass of one atom of an element is 6.645 x 10-23g. How many moles of element are there in 0.320 kg.

14. What is the most essential conditions that must be satisfied in a redox reaction?

15. Calculate the empirical and molecular formula of a compound containing 76.6% carbon, 6.38 % hydrogen and rest oxygen its vapour density is 47

16. Mixture of salt and water is a solution while that of oil and water is not. Explain

17. Calculate the mass of the following: 1 atom of silver

18. 4 x 5 = 20
19. A Compound on analysis gave Na = 14.31% S = 9.97% H= 6.22% and 0= 69.5% calculate the molecular formula of the compound if all the hydrogen in the compound is present in combination with oxygen as a water of crystallization. (molecular mass of the compound is 322).

20. Write note on decomposition reaction

21. Balance the following equations by oxidation number method.
P + HNO3 ⟶ HPO3 + NO + H2O

22. An organic compound was found to contain carbon = 40.65%, hydrogen = 8.55% and Nitrogen = 23.7%. Its vapour density was found to be 29.5. What is the molecular formula of the compound?