Chemistry Delhi (Set 2)

General Instructions:

Read the following instructions very carefully and strictly follow them:

1. Question paper comprises four sections - A, B, C and D.
2. There are 37 questions in the questions paper. All questions are compulsory.
3. Section - A: Q. No. 1 to 20 are very short answer type questions carrying one mark each. Answer these questions in one word or one sentence.
4. Section - B: Q. No. 21 to 27 are short answer type questions carrying two marks each.
5. Section - C: Q. No. 28 to 34 are long answer type-I questions carrying three marks each.
6. Section - D: Q. No. 35 to 37 are long answer type-II questions carrying five marks each.

1. There is NO overall choice in the question paper. However an internal choice has

been provided in 2 questions of two marks, 2 questions of three marks and all the 3 questions of five marks. You have to attempt only one of the choices in such questions.

1. However, separate instructions are given with each section and question, wherever necessary.
2. Use of calculators and log tables is NOT permitted.

Read the given passage and answer the question follow:

The halogens have the smallest atomic radii in their respective periods. The atomic radius of fluorine is extremely small. All halogens exhibit – 1 oxidation state. They are strong oxidising agents and have maximum negative electron gain enthalpy. Among halogens, fluroine shows anomalous behaviour in many properties.

For example electro negativity and ionisation enthalpy are higher for fluorine than expected whereas bond dissociation enthalpy, m.p and b.p and electron gain enthalpy are quite lower than expected. Halogens react with hydrogen to give hydrogen halides (HX) and combine amongst themselves to form a number of compounds of the type XX', XX'₃, XX'₅ and XX'₇ called inter-halogens.

Question 1

Why halogens have maximum negative electron gain enthalpy?

Solution:

Due to the smallest size of halogens in their respective periods, the value of Zeff is maximum hence the negative value of electron gain enthalpy is maximum.

Read the given passage and answer the question follow:

The halogens have the smallest atomic radii in their respective periods. The atomic radius of fluorine is extremely small. All halogens exhibit – 1 oxidation state. They are strong oxidising agents and have maximum negative electron gain enthalpy. Among halogens, fluroine shows anomalous behaviour in many properties.

For example electro negativity and ionisation enthalpy are higher for fluorine than expected whereas bond dissociation enthalpy, m.p and b.p and electron gain enthalpy are quite lower than expected. Halogens react with hydrogen to give hydrogen halides (HX) and combine amongst themselves to form a number of compounds of the type XX', XX'₃, XX'₅ and XX'₇ called inter-halogens.

Question 2

Why fluorine shows anomalous behaviour as compared to other halogens?

Solution:

Fluorine shows abnormal behavior due to its very small size.

Read the given passage and answer the question follow:

The halogens have the smallest atomic radii in their respective periods. The atomic radius of fluorine is extremely small. All halogens exhibit – 1 oxidation state. They are strong oxidising agents and have maximum negative electron gain enthalpy. Among halogens, fluroine shows anomalous behaviour in many properties.

For example electro negativity and ionisation enthalpy are higher for fluorine than expected whereas bond dissociation enthalpy, m.p and b.p and electron gain enthalpy are quite lower than expected. Halogens react with hydrogen to give hydrogen halides (HX) and combine amongst themselves to form a number of compounds of the type XX', XX'₃, XX'₅ and XX'₇ called inter-halogens.

Question 3

Arrange the hydrogen halides (HF to HI) in the decreasing order of their reducing character.