Explore topic-wise InterviewSolutions in Current Affairs.

(a) White coloured insoluble calcium carbonate is formed.
(b) Carbon dioxide is evolved due to the chemical reaction between acetic acid and sodium hydrogencarbonate.

True 

Internet telephony uses the technology Voice over Internet Protocol (VoIP), which makes it possible for integrating telephone services into computer networks.

True 

The World Wide Web (WWW) is a way of exchanging information between computers on Internet. It tries to tie a vast collection of information together so that users can access it according to their need.

True 

It has such type of tendency because it makes possible for media organisations deliver text, audio and video material over the same wired and wireless connections.

(c) Internet telephony is having the VoIP feature which enables it to make a long distance call free of cost.

Correct option  (A) lt is halved. 

Explanation:

The speed of rotation affects the frequency and voltage output. When the speed of rotation is reduced by half, the frequency and the voltage output are reduced by half as well.

An input device is used to enter data or information into the computer for processing, e.g. a keyboard. 

OCR is an input device used to convert handwritten text into machine readable format. It reads the characters with the help of a light source and photoelectric cells. 

The technology is being developed for greater accurate recognition which is also known as Intelligent Character Recognition (ICR).

Iron is essential for forming haemoglobin in the blood.

1. The solution may be neutral or acidic. 

2. Red litmus remains unchanged when dipped in acidic solution or neutral solution.

(i) (b) and (c) statements are true. 

(ii) Keyboard, mouse, joystick, light pen and touch screen.

(c) Assertion is true, but reason is false.

Correct Reason: Such samples are basic in natural.

Correct option is D) Red

The turmeric paper turns red when basic substances come in touch with the turmeric paper.

When lime water is added to turmeric the colour changed to red.

(a) When carbon dioxide is passed through lime water, it turns milky due to the formation of Calcium carbonate (CaCO3).
(b) The chemical name of baking soda is Sodium bicarbonate (NaHCO3).
(c) Two methods by which rusting of iron can be prevented are greasing and galvanization.
(d) Changes in which only physical properties of a substance change are called physical changes.
(e) Changes in which new substances are formed are called chemical changes.

a) Indicators show different colours in acidic and basic solutions. 

b) Sodium hydroxide turns red litmus blue. 

c) Tooth decay is caused by the presence of acid.

Correct option is B) Blue

Correct option is B) Basics

Correct option is A) Turmeric

1. Curd contains lactic acid. The lactic acid makes curd rice sour in taste.

2. Lemon juice contains citric acid. The citric acid makes lemon rice sour in taste.

3. Generally acids are sour in taste.

1. Take a natural acid say lemon juice in six test tubes and add Copper, Zinc, Magnesium, Iron, Brass, Aluminium pieces to each one of the test tubes separately. 

2. Note the observations. 

3. Light a matchstick and introduce it into the test tubes. 

4. The gas releasing catches fire with a sound. 

5. This gas is Hydrogen. This is the test for the presence of Hydrogen.

1. Turmeric indicator is one of the natural indicator. 

2. By adding small amount of water to turmeric powder, a paste is prepared. 

3. This is applied on a blotting paper or filter paper and dried.

4. These strips are used as indicators to find the nature of the solution. 

5. In acidic solution, turmeric indicator paper has no change in colour. 

6. That means, it remains yellow. In basic solution, the colour changes from yellow to red.

1. Acidity arises due to hydrochloric acid present in the stomach. 

2. Acidity results in indigestion and a burning sensation in the stomach. Even it may cause headache. 

3. To treat acidity doctors give antacids. These will give relief from acidity and indigestion. 

4. Antacids contain sodium hydrogen carbonate. When these antacids are taken orally, they react with the hydrochloric acid present in the stomach and reduces its strength. 

5. Milk of magnesia is one such antacid. 

6. Eating at irregular intervals, skipping meals and eating too quickly are more reasons. Certain foods like tomatoes, lime juice, and oranges could also lead to acidity. 

7. Lack of exercise and stress also results in acidity or heart burn. Hence, the best way to avoid acidity is to avoid the factors that cause it. 

8. It is a must to avoid fried and oily foods, and one must drink plenty of water, at least 8-10 glasses everyday. 

9. Yogurt helps in easy digestion of food.

1. Take half a beaker full of water. Add about 5 gm of lime that we apply to betel leaves. 

2. Stir the beaker well and let it stand overnight. 

3. Filter this solution the following day. 

4. This filtrate is lime water. This solution should be transparent. 

5. We use this filterate in our experiments. 

6. Lime is used when we consume betel leaves.

The sun’s rays do not fall perpendicularly at all the places on the earth because the earth is not flat but spherical in shape.

Our country lies in the northeastern hemisphere.

The earth takes 365 days and 6 hours to complete one revolution.

We brush our teeth with tooth paste because it is basic

Chemical name:

Sodium hydrogencarbonate 

Formula: NaHCO₃ .

The term orbital motion is used to describe the earth’s revolution around the sun.

Day and night occur on the earth because of the earths rotation.

(a) 'X' is CH₃COOH and 'Y' is CH₃-COOCH₂CH₃.

(b) CH₃COOH + C₂H₅OH+H₂SO₄ → CH₃COOC₂H₅+H₂O

Correct option is  D) C₂H₂

Hard water contains salts of Ca and Mg. Soap molecule reacts with these salts to produce white precipitate called scum, which is insoluble in water and the cleansing action of soap becomes ineffective.

Soap molecules form micelles where the ionic end of soap, dissolves in water while the carbon chain dissolves in oil. The emulsion in water thus formed helps in dissolving the dirt in water and we can wash our clothes clean.

Since carbon has a valency of four, it is capable of bonding with four other atoms of carbon or atoms of some other monovalent elements. In order to satisfy its tetravalency carbon can form double or triple bonds also with other C-atoms or with oxygen, nitrogen etc. 

Reasons for carbon forming a large number of compounds are: 

(i) Catenation: Carbon has the unique property or ability to form bonds with other atoms of carbon, giving rise to large molecules. This property is called catenation. These compounds may have long chains of carbon, branched chains of carbon or even carbon atoms arranged in rings. 

(ii) Tetravalency: Carbon has four valence electrons in its valence shell so the valency of carbon is four. Due to this valency, carbon is a tetravalent element and it has the capability of satisfying its tetravalent by sharing its electrons with some monovalent elements and forming covalent bonds.

(iii) Carbon exhibits catenation much more than any other element due to its smaller size which makes the C - C bonds strong while the bonds between any other element are comparatively weaker due to its large size.

(i) Bromoethane

(ii) Methanol

(iii) Hexane.

It is half of the distance of radius of each atom.

Though both electronegativity and electron affinity refers to the attraction of electron but is used in different context. Electronegativity refers to the attraction of the bonding electron or a shared pair of electron whereas electron affinity refers to the attraction of electron by isolated gaseous atoms.

Half of the distance between length of covalent bond is called covalent radius.

The tendency of metals to remain positive ions in compounds is called electropositive character. (OR) The tendency of an atom to lose electrons to form positive ions.

Atomic radius is measured in pico meter (pm) units. 

1 pm = 10¹² m

1. c. the same number of protons, but different numbers of neutrons.

2. d. 3

3. b. U

4. a. Any of several species of the same chemical element with different masses whose nuclei are unstable

5. a. TRUE

1. All the known elements could not be arranged in the form of triads. 

2. The law failed for very low mass or for very high mass elements. Eg : In case of F, Cl, Br the atomic mass of Cl is not an arithmetic mean of atomic masses of F and Br. 

3. As the techniques improved for measuring atomic masses accurately, the law was unable to remain strictly valid.

The electronic configuration of an atom conveys the valence electrons and number of shells. Valence electrons helps in detecting the group number. 

Number of shells in an atom tells the period to which it belongs.

The 6^th period consists of elements that have atomic numbers 58 to 71. They are called Lanthanides. The 7^th period consists of elements that have atomic numbers 90 to 105. They are called Actinides. Both of them are called inner transition elements. Lanthanides and actinides are not accommodated in the main body of the periodic table but are placed in separate rows in form of two series at the bottom of the modern periodic table. The 7^th period is an incomplete period as it has only 23 elements.

Electronegativity :

The electronegativity of an element is defined as the relative tendency of its atom to attract electrons towards itself when it is bounded to the atom of another elements.

Various methods to calculate Electronegativity : 

1) Milliken Scale : According to Milliken, the electronegativity of an element is the average value of its ionization energy and electron affinity. 

2) Pauling Scale : Pauling scale is based on bond energies. The electronegativity of hydrogen is assumed as 2.20. Electronegativity of other elements is calculated with respect to hydrogen.