Explore topic-wise InterviewSolutions in Current Affairs.

The electron gain enthalpy is the molar enthalpy change when an isolated gaseous atom (or anion) in its ground state adds an electron to form the corresponding anion. Thus, the enthalpy change for the research.

X (g) + e^- → X^- (g)

is called the electron gain enthalpy (Δ_egH) of the element X.

Citrus fruits contain an acid called citric acid. Lemon, orange are examples of citrus fruits. They also contain ascorbic acid which is commonly known as Vitamin C. In short, the chemical compound found in citrus fruits is acidic in nature.

Lime water is a solution of calcium hydroxide (Ca(OH)₂). When CO₂ gas is passed through lime water, the following reaction occurs. 

Ca(OH)₂ + CO₂ → CaCO₃↓ + H₂O

                      (white precipitate)

The solution of lime water turns milky due to the formation of calcium carbonate, which is a white precipitate insoluble in water.

If CO₂ gas is passed in excess amounts, then the above reaction occurs further. 

CaCO₃↓ + H₂O + CO₂ → Ca(HCO₃)₂

                                     (soluble in water)

The product formed is calcium hydrogen carbonate, which is soluble in water. Hence the milky solution becomes a clear solution.

2CaOCl₂(s) + H₂SO₄(aq) → CaSO₄(aq) +CaCl₂(aq) + 2HCIO(aq)

HCIO →  HCI + [O]

HCIO-Hypochlorous acid    

[O]-Nascent oxygen

Coloured Substance + [O]→Colourless.

(a). When CO₂ is passed through lime water in a limited quantity than calcium carbonate gets precipitated as a white colour mass at the bottom of the test tube according to the following reaction: -

Ca(OH)₂ + CO₂→ CaCO₃ + H₂O

(b). When CO₂ is passed through lime water in excess then the white precipitate initially formed gets dissolved forming Ca(HCO₃)₂ which is soluble in water as per the following reaction: -

CaCO₃ + H₂O + CO₂→ Ca(HCO₃)₂

Quantity of OH⁺ ion increases.

Correct option: (B) O_2(g) + 2H_2(g) → 2H₂O_(g) 

Common salt or Sodium Chloride is used in the manufacturing process of a variety of other salts like washing soda, bleaching powder, slaked lime etc.

Lime juice contains citric acid which imparts a sour taste to it while lime water is alkaline and hence bitter to taste.

An acid combines with alkali to nullify their individual properties. Such reactions are called neutralization reaction.

Quantity of H⁺ ion increases.

a) 

Non-metal a is nitrogen because it is the largest constituent of air which constitute around 78% of the gases.

• B is Ammonia, 
• C is Nitrogen dioxide 
• D is Nitric acid. 

When heated with H₂ in 1:3 ratio in the presence of catalyst (Fe) following reaction takes place. 

3N₂ + 3H₂ → 2NH₃ 

On heating Nitrogen with O₂ it gives nitrogen-di-oxide 

N₂ + 3O → 2NO₂ 

When nitrogen dioxide is passed into water in the presence of air it gives an Nitric acid 

NO₂ + H₂O → HNO₃ 

b) Nitrogen belong to group 15

PVC: Carbon, hydrogen, chlorine

Polythene: Carbon, hydrogen Carbon, hydrogen, oxygen, nitrogen, chlorine are nonmetals

(i) Non-metals are electron accepters, they cannot supply electrons so as to convert H⁺ ion to H₂(g).

(ii) Like metals, hydrogen can lose an electron to form positive H⁺ ion.

(iii) Aluminium is covered with a strong Protective layer of oxide which protects the metal from further corrosion.

In the periodic table, elements are placed according to their electronic configuration. If an element has only one shell in its electronic configuration, it is placed in the first period. If the element has two shells then it is placed in the second period, and so on. Vertical columns in the periodic table are called groups.

There are eighteen groups and in a group, all the elements have the same number of valence electrons.

Correct option  (A) (i), (ii) and (iii) only 

Explanation:

 Element after Q (silicon) is phosphorus which is a non-metal. Element R is arsenic which is a metalloid. Element just before R (arsenic) is germanium which is a metalloid. Element just before S (tellurium) is antimony which is also a metalloid.

a) A is Carbon. B is Carbon monoxide C is Carbon-dioxide 

b) Group 14

Most of the human body is made of water (H₂O). It is not surprising that majority of a human body’s mass is oxygen. Carbon, the basic unit of organic molecules is the second. 99% of human body is made up of just six elements. Oxygen (65%), carbon (18%), hydrogen (10%), nitrogen (3%), calcium (1.5%), phosphorous (1%). Which shows our body has almost 97% of nonmetals. So we may consider our body as non-metal.

(i) A will have least number of carbon atoms. 

(ii) C will have maximum number of carbon atoms.

(B) P-(iii), Q-(i), R-(ii), S-(iv) 

Correct option is B) 6

(a) Zn(s) + 2HCl →ZnCl₂(aq) + H₂(g)

ZnCl₂(aq)- Zinc chloride

(b) Zn(s) + NaOH → Na₂ZnO₂ + H₂  

Na₂ZnO₂  -Sodium Zincate

Correct option  (B) ll, lll and lV only 

Explanation: 

AI becomes passive if it is dipped in nitric acid due to formation of a protective layer of aluminium oxide. Carbon cannot reduce the oxides of Na or Mg 

NaCl is a good conductor of electricity in molten state or in aqueous solution.

Metals like K, Ca and Mg are highly reactive and are never found in free state in nature.

Inorganic or Minerals acids are derived from minerals occurring in nature.

Some common acids that are found in laboratories are

Hydrochloric acid (HCl),

Sulphuric acid (H₂SO₄) and

Nitric acid (HNO₃).

Some of the lesser used acids are

Acetic acid (CH₃COOH),

Hydrofluoric acid (HF), Hydrofluoric acid is a highly corrosive acid and is used to etch glass.

Carbonic acid (H₂CO₃).

Correct option is D) Litmus paper

(a) Oxyacids: - HNO₃, H₂SO₄

(b) Hydracid:- HCl, HBr

(c) Monobasic acid:- HCl, HBr

(d) Dibasic acid: - H₂SO_{4 ,} H₂CO₃

(e) Tribasic acid:- H₃PO₄, H₃PO₃

B) Some metals react with HCl releasing hydrogen gas.

Organic acids – Those acids which are derived from plants,

e.g., citric acid, acetic acid, tartaric acid.

Inorganic acids – Acids derived from minerals 

e.g. HCl₂ ,H₂SO₄ 

Hydracids – Acids containing hydrogen and a non-metallic element other than oxygen,

e.g. HCl, HBr, HI.

Oxyacids – Acids containing hydrogen, another element and oxygen,

e.g. HNO₃ , H,SO₄

Since metals produce ringing sounds, they are said to be Sonorous.

X— NaOH (Sodium hydroxide) 

A— Na₂ZnO₂ (Sodium zincate) 

B— NaCl (Sodium chloride) 

C— CH₃COONa (Sodium acetate

A substance which cannot be broken down further by chemical reactions, by cooling, heating, or by electrolysis, is called Element.

Strength of acids depends upon concentration of hydronium ion |H₃O⁺| present in an aqueous solution of an acid. Strength of alkali depends on the concentration of the hydroxyl ions |OH^–| present in an aqueous solution of an alkali.

Greater the value of ‘a’, more easily the gas is liquefiable. Similarly, greater the value of V, greater is the molecular size. Hence, gas Y will be more easily liquefiable and will have greater molecular size.

Effusion is the process of diffusion taking place from a tiny hole.

(i) Pascal second, (ii) Nm¹

(KE)nmoles = 3/2 × nRT; 

n = 2; T = 300 K 

= 3/2 × 2 × 8.314 × 300 = 7482.0 J

(KE) n mole = 3/2 × nRT 

T = 273K n = 320g/64g = 5 

3/2 × 5 × 8.314 × 273 = 17020 J

pV = {2.9 g}/{M} x R x 368 K

Also pV = {0.184 g}/{2 g/mol} x R x 290 K

From these equations, we can write

{2.9 g}/{M} x R x 368 K = {0.184 g}/{2 g/mol} x R x 290 K

or, M = {2.9 g x 2 g/mol x R x 368 K}/{0.184 g x R x 290 K}

= 40 g/mol

The amount of substance that contains the same number of entities(atoms, molecules, ions or other particles) as the number of atoms present in 12g of carbon-12 isotope.

0.50 m Na₂CO₃ solution means that 0.5 mol (or 53g) of Na₂CO₃ are present in 1000 g of solvent. 

0.50 M Na₂CO₃ solution means that 0.5 mol (or 53g) of Na₂CO₃ are present in 1L of a solution. 

(a) It is the parts of a component or solute per million parts of the solution. 

(b) The mass% of a component in a given solution is the mass of the component per 100 g of the solution.

इस्पात के यान्त्रिक गुण उसके ऊष्मा उपचार पर निर्भर करते हैं। ऊष्मा उपचार द्वारा इस्पात को कठोर या नर्म बनाया जा सकता है। 

इस्पात का कठोरीकरण – इस्पात को रक्त-तप्त ताप तक गर्म करके ठण्डे जल द्वारा उसे एकाएक ठण्डा करने की क्रिया इस्पात का कठोरीकरण (hardening of steel) कहलाती है। इस क्रिया से इस्पात बहुत कठोर और भंगुर हो जाता है। 

इस्पात का टैम्परीकरण – कठोरीकृत (hardened) इस्पात को किसी उच्च ताप तक (पहले से कम ताप पर) पुनः गर्म करके धीरे-धीरे ठण्डा करने की क्रिया इस्पात का टैम्परीकरण (tempering) कहलाती है। इस क्रिया से इस्पात नर्म (soft) हो जाता है और उसकी भंगुरता (brittleness) मिट जाती है। इस्पात को धीरे-धीरे ठण्डा करने पर ऑस्टीनाइट धीरे-धीरे सीमेन्टाइट और आइरन में अपघटित हो जाता है, जिससे इस्पात नर्म हो जाता है।

धातुओं के ऑक्साइडों को ऐलुमिनियम चूर्ण के साथ उच्च ताप पर गर्म करने से धातुएँ प्राप्त होती हैं। यह क्रिया ऊष्माक्षेपी है तथा इसको एलुमिनोथर्मिक विधि कहते हैं। 

3 Co₃O₄ + 8 Al → 9 Co + 4Al₂O₅ 

3 Mn₃O₄ + 8 Al → 9 Mn + 4 Al₂O₅ 

इस विधि का उपयोग CO, Mn और Cr धातुओं के निष्कर्षण और थर्माइट वेल्डिंग में किया जाता है।

• पीतल– Cu (80%), Zn (20%) 

• उपयोग– इसका उपयोग बर्तन बनाने में किया जाता है।

1. सफेद वर्णक (pigment) के रूप में तथा 

2. क्रीम, पाउडर और टूथपेस्ट बनाने में।

Correct option : (2) 3.33 Å

Explanation: 

Since the electron is in ground state which implies that electron is in the first orbit of hydrogen atom with radius 0.53 Å. For first orbit the circumference of the orbit 2πr is the deBroglie wavelength. 

Hence λ = 2πr = 2 x 0.53 x π = 3.33 Å

The correct answer is (B) 33