Explore topic-wise InterviewSolutions in Current Affairs.

(c) Carbon dioxide

(a) Glucose = C₆H₁₂O₆ (Polyatomic molecule)

(b) Helium = He (Monoatomic molecule) 

(c) Carbon dioxide = CO₂

(Triatomic molecule) 

(d) Hydrogen = H₂ (Diatomic molecule)

So, (c) is the correct answer

(b) 1 atom of He

The volume occupied by 3 moles of HCl gas at STP is 67.2 L

The mass percentage of hydrogen in ethane (C₂H₆) is 20%

(b) 2.24 litre

(b) 14 amu

Atomic mass of Nitrogen is 14.00674 grams. It is equal to 1 mole of Nitrogen atoms. 

So, answer (b) is correct.

Gram molar mass of NaCl = 23 + 35.5 

= 58.5 g 

1000 g of NaCl costs = Rs 18 

∴ 58.5 g of NaCl costs = \(\frac{18}{1000}\times58.5\)

= Rs 1.053 

The cost of one mole of NaCl = Rs 1.053

(c) 1/12 th of the mass of a C – 12 atom

The molecular mass of water (H₂O) is 18. 

18 g of water molecule = 1 mole. 

0. 18 g of water = \(\frac{1}{18}\) x 0.18 = 0.01 mole. 

1 mole of water (Avogadro’s number) contains 6.023 × 10²³ water molecules.

0. 01 mole of water contain \(\frac{6.023\times10^{23}}{1}\) x 0.01 = 6.023 × 10²¹ molecules.

1 mole of nitrogen (28 g) + 

3 moles of hydrogen (6 g) → 

2 moles of ammonia (34 g)

(b) 4 moles of C

Answer is (b) 54

The salient features of “Modem atomic theory” are, 

1. An atom is no longer indivisible. 

2. Atoms of the same element may have different atomic mass. 

3. Atoms of different elements may have the same atomic masses. 

4. Atoms of one element can be transmuted into atoms of other elements. In other words, an atom is no longer indestructible. 

5. Atoms may not always combine in a simple wholenumber ratio. 

6. Atom is the smallest particle that takes part in a chemical reaction.

7. The mass of an atom can be converted into energy [E = mc²].

Carbon – 12 is the standard while measuring the atomic masses. Because no other nuclides other than C – 12 have exactly whole-number masses in this scale. This is due to the different mass of neutrons and protons acting to change the total mass in nuclides with proton/neutron ratio other than 1 : 1 ratio of carbon – 12.

A. (ii) 

B. (iii) 

C. (i) 

D. (v) 

E. (iv)

(a) One gram of C – 12 contains Avogadro’s number of atoms.

12 g of Carbon contains 6.023 × 10²³ atoms, 1 g of Carbon contain \(\frac{6.023\times10^{23}}{12}\) = 5.018 x 10²² atoms and its is not Avogadro’s number of atoms. 

So (a) is the incorrect statement.

(b) 20 protons and 20 neutrons

1. same, different

2. neutrons 

3. artificial transmutation 

4. mass number 

5. standard atomic weight 

6. 1.008 

7. homo 

8. atomicity 

9. 22, 400 

10. four

(c) 32 g 

By definition, the gram molecular mass of oxygen molecule O₂ is 32 g. 

So the answer (c) is correct.

(c) 22.4 litre

A. (iii) 

B. (i) 

C. (iv) 

D. (v) 

E. (ii)

The relative atomic mass of magnesium-based on C – 12 scale is 24

The mass of proton or neutron is approximately 1 amu

(b) 12.011 amu

The vapour density of a gas is 32. Its relative molecular mass will be 64

A. (iv) 

B. (v) 

C. (ii)

D. (iii) 

E. (i)

1. 11.2 L 

2. 3 × 6.023 × 10²³ 

3. molecules

4. E = me² 

5. empirical, molecular

(d) Phosphorous.

Correct answer is (a) Thermoreceptor

Small Particles of calcium salts in the ears of vertebrates are called otolith.

Correct answer is (c) Pars nervosa

Correct answer is (d) sense organs

Correct answer is (b) sacculus and utriculus

Correct answer is (d) tongue

Correct answer is (b) limbic system

Occipital lobe of the fore-brain is for sight whereas olfactory lobe is for sense of smell.

The structural and functional unit of nervous system, i.e. neuron with their functions are as 

• Cell body: Stimulus received from dendrite is changed into impulse in the cyton. 
• Dendrites: They receive sensation or stimulus, which may be physical or chemical. 
•  Axon: It conducts impulse away from the cell body

Effectors are nothing but the muscles itself. If it is absent then the movement of the hand after receiving the signal won’t be possible since there is no organ to act upon the electric impulse. For example, in case we touch hot pan then in the absence of effectors, we won’t be able to pull back our hand.

(a) Hormones are made by endocrine glands.  

(b) Receptors are the special cells present in our sense organs which detect all the information  from our environment and feed it to the nervous system. An effector responds to electrical  impulses sent from the nervous system through motor nerves.

1. (ii) Stomach

2. (i) TRUE

3. (iii) Pancreas

4. (i) Large quantities of sugar in the blood

5. (ii) FALSE

1. (iii) Target organs

2 (ii) False

3. (i) TRUE

4. (ii) Chemical messangers

5. (i) TRUE

Correct answer is (c) hypothalamus

1. Structure of midbrain:

• Midbrain is the middle part of the brain situated between the forebrain and the hindbrain. It is present between the pons varolii and diencephalon. 
• It has two distinct regions : Corpora quadrigemina and crura cerebri. 
• Corpora quadrigemina consists of two pairs of lobes, viz., superior colliculi and inferior colliculi. These are located in the thick wall of midbrain. 
• Crura cerebri are thick bands of longitudinal nerve fibres, present on the floor of midbrain.

2. Functions of midbrain:

• Inferior colliculi control and coordinate auditory reflexes. 
• Superior colliculi control head and eye movements. 
• Crura cerebri connect the cerebrum to cerebellum and spinal cord.

1. (i) TRUE

2. (ii) FALSE

3. (i) TRUE

4. (i) TRUE

5. (i) TRUE

Structure of cerebrum:

1. Cerebrum is the largest part of the brain. It forms 80-85% volume of the brain. 

2. A median longitudinal fissure divides the cerebrum into two cerebral hemispheres. These hemispheres are interconnected by a thick band of transverse nerve fibres called corpus callosum. 

3. The outer part of cerebrum is called cerebral cortex while the inner part is called cerebral medulla. 

4. The roof of cerebrum is called pallium. Pallium is highly folded forming sulci and gyri. Sulci are depressions while gyrl are ridges. The gyri increase the surface area of cerebral cortex. 

5. The ventro-lateral walls of cerebrum are thickened and are called corpora striata. 

6. The cerebral cortex has three deep sulci, the central, lateral and parieto-occipital.

7. These sulci divide the cerebral hemisphere into four lobes. These are frontal, parietal, occipital and temporal lobes. A fifth median lobe called insula or insular cortex is folded deep within the lateral sulcus. 

8. The central sulcus separates frontal and parietal lobes, the lateral sulcus separates parietal and temporal lobes and the parietooccipital sulcus separates parietal and occipital lobe.

(a) Spinal cord is a cylindrical structure which begins in continuation with medulla and extends downwards. Its function is the conduction of nerve impulses to and from the brain and it is concerned with spinal reflex actions. 

(b) The medulla controls various involuntary actions such as heart beat, breathing, blood pressure and peristaltic movements of the elementary canal. It is also the controlling centre for reflexes such a swallowing, coughing, sneezing, secretion of saliva and vomiting.

Structure of hindbrain:

1. Hindbrain includes cerebellum, pons varolii and medulla oblongata. 

2. Cerebellum is 11% of the total brain and is the second largest part of the brain. 

3. It has three lobes, median vermis and lateral two cerebral hemispheres. It has outer grey and inner white matter. 

4. Cerebral cortex shows sulci and gyri. The inner white matter of cerebellar medulla shows arbor vitae or branching tree-like processes. 

5. Pons is the part that connects the two cerebral hemispheres. It has outer white and inner grey matter. Pons is made up of nerve fibres which form bridges between cerebrum and medulla oblongata.

6. Medulla oblongata is the last part of the hindbrain which continues further as a spinal cord. It has outer white and inner grey matter. 

7. Its roof shows has posterior choroid plexus. 

8. Eight pairs of cranial nerves arise from medulla oblongata.

Functions of spinal cord:

1. Spinal cord is the main pathway for conduction of sensory and motor nerve impulses. 

2. The sensory impulses travel from the body to the brain and the motor impulses travel from the brain to the body. 

3. Spinal reflexes are controlled by spinal cord. 

4. The spinal cord reduces the load on the brain by taking appropriate actions in a reflex way.

(a) Hindbrain has 3 regions: 

(i) Pons: It takes part in regulating respiration. 

(ii) Cerebellum: It helps in maintaining posture and balance of the body. It enables us to make precise and accurate movements. 

(iii) Medulla: The medulla controls various involuntary actions such as heart beat, breathing, blood pressure and peristaltic movements of the elementary canal. It is also the controlling centre for reflexes such a swallowing, coughing, sneezing, secretion of saliva and vomiting. 

(b) Function of cerebrum: It is the main thinking part of the brain. It is the site of our faculties such as learning, reasoning, intelligence, personality and memory. All our thoughts, sensation, actions and movements are controlled by cerebrum.

All other statements except (ii) and (iii) are incorrect because forebrain is responsible for thinking process and cerebellum controls posture and balance of the body. Statement (ii) and (iii) are true in their sense. Therefore, correct option is (c) (ii) and (iii).