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Question of Exercise 2

Thermodynamics of Class 11

Question

One mole of graphite and diamond were separately burnt to form CO2 gas. The ΔH° values of the two reactions are given below:

C(graphite) + O2(g) ⎯→ CO2(g) ; ΔHº = – 393.5 kJ

C(diamond) + O2(g) ⎯→ CO2(g) ; ΔHº = – 395.4 kJ

Choose the correct statement.

 

Answer

Option 1 Graphite is more stable than diamond.

Option 2 Diamond is more stable than graphite.

Option 3 Graphite has greater affinity for oxygen.

Option 4 Diamond has greater affinity for oxygen.

Frequently Asked Questions

Li shows diagonal relationship with

A: Mg

B: Be

C: Al

D: B

 

Solution:

Explanation:

Diagonal relationship between elements refers to the relationship between diagonally adjacent elements in the second and third periods due to similarity in their size.

Lithium is different from other alkali metals due to its small size but since its size resembles with that of magnesium, it shows a diagonal relationship with magnesium.

Final Answer:

The correct option is A: Mg

 

How many moles of magnesium phosphate

Mg3(PO4)2will contain 0.25 mole of oxygen atoms ?

pic40

 

Solution:

Explanation:

phosphate

Final Answer:

The correct option is B: 3.125×10 -2.

 

Draw the molecular structure of

N2O5.

Solution:

Explanation:

molecular structure

 

Aqueous solution of borax is

A: neutral

B: amphoteric

C: basic

D: acidic

 

Solution:

Explanation:

Borax (Na[ B4O5(OH)4].8H2O) is a salt of boric acid (H3BO3) and sodium hydroxide (NaHO) base.

Borax, also called sodium borate, sodium tetraborate or disodium tetraborate is basically a salt of weak acid and a strong base.

Borax, when dissolved in water, ionizes and hydrolysis of borate ion formed gives HO- and boric acid.

Since boric acid is weak acid and sodium hydroxide is strong, the aqueous solution is alkaline in nature.

Final Answer:

The correct answer is C: basic

 

The most abundant element in the universe is

A: helium

B: oxygen

C: silicon

D: hydrogen

 

Solution:

Explanation:-

  • Hydrogen is the most abundant element in the universe; it is present in every Star.
  • Two hydrogen atoms fuse together to form Helium atom and this Helium atom is the second most abundant element.
  • Oxygen is the third most abundant element .

Final Answer:-

The most abundant element in the Universe is  (D) hydrogen 

 

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