D. Monopotassium tartarate<\/td> 4. Gun Powder<\/td><\/tr><\/tbody><\/table><\/div><\/figure>\n\n\n\nCodes<\/strong><\/p>\n\n\n\nA B C D<\/p>\n\n\n\n
(a) 2 4 1 3<\/p>\n\n\n\n
(b) 2 4 3 1<\/p>\n\n\n\n
(c) 4 2 3 1 <\/p>\n\n\n\n
(d) 4 2 1 3<\/p>\n\n\n\n
<\/span>Ans. (a)<\/strong><\/span><\/h3>\n\n\n\nPotassium bromide (KBr): This compound, along with silver bromide (AgBr), is used in developing photographs from negative films. It enhances the contrast of a photograph, typically a black and white photograph.<\/p>\n\n\n\n
Potassium nitrate (KNO3<\/sub>): This compound contains potassium (K), nitrogen (N), and oxygen (O). Upon heating, it releases a significant amount of oxygen. Since oxygen is essential for combustion, the presence of KNO3<\/sub> in large amounts leads to explosive combustion of other substances. Hence, KNO3<\/sub> is used in gunpowder.<\/p>\n\n\n\nPotassium sulfate (K\u2082SO\u2084): It serves as an excellent source of potassium (K) and sulfur (S), both of which are essential for the growth of plants in substantial quantities. As a result, these two elements are categorized as macronutrients, necessary in large amounts. Consequently, K\u2082SO\u2084 finds application in the synthesis of fertilizers.<\/p>\n\n\n\n
Monopotassium tartrate (KC4<\/sub>H\u2082O): Also known as potassium bitartrate or cream of tartar, this compound, along with baking soda (NaHCO3<\/sub>), constitutes the composition of baking powder. It enhances the activity of baking soda, leading to increased puffiness in baked goods.<\/p>\n\n\n\n<\/span>Q5. Consider the following statements. (1998)<\/strong><\/span><\/h2>\n\n\n\nCoke is one of the materials of the charge added to blast furnace for the production of steel\/iron. Its function is to<\/em><\/p>\n\n\n\n1. act as reducing agent.<\/p>\n\n\n\n
2. remove silica associated with the iron ore.<\/p>\n\n\n\n
3. function as fuel, to supply heat.<\/p>\n\n\n\n
4. act as an oxidising agent.<\/p>\n\n\n\n
Select the correct answer using the codes given below.<\/em><\/p>\n\n\n\n(a) 1 and 2 are correct<\/p>\n\n\n\n
(b) 2 and 4 are correct<\/p>\n\n\n\n
(c) 1 and 3 are correct<\/p>\n\n\n\n
(d) 3 and 4 are correct<\/p>\n\n\n\n
<\/span>Ans. (c)<\/strong><\/span><\/h3>\n\n\n\nStatements (1) and (3) are correct. Coke is considered a reducing agent as it facilitates the reduction of metal oxides. Derived from the incomplete combustion of wood, coke is predominantly composed of nearly pure carbon. The carbon content in coke exhibits a strong affinity for oxygen when combined with metals in the form of metal oxides. Consequently, the metal oxide loses oxygen, a process termed reduction. Additionally, coke serves as a fuel and combusts to generate high temperatures in the furnace.<\/p>\n\n\n\n
<\/span>Q6. Assertion (A) Sodium metal is stored under kerosene. Reason (R) Metallic sodium melts when exposed to air. (1998)<\/strong><\/span><\/h2>\n\n\n\nCodes<\/strong><\/p>\n\n\n\n(a) Both A and Rare true and R is the correct explanation of A<\/p>\n\n\n\n
(b) Both A and R are true but R is not the correct explanation of A<\/p>\n\n\n\n
(c) A is true but R is false<\/p>\n\n\n\n
(d) A is false but R is true<\/p>\n\n\n\n
<\/span>Ans. (c)<\/strong><\/span><\/h3>\n\n\n\nSodium metal is typically stored in kerosene due to its significant reactivity with both oxygen and moisture. Contrary to popular belief, it does not melt when it reacts with water or air; instead, it forms sodium hydroxide or oxide. Sodium, which belongs to group I and the third period, is classified under the s-block of the periodic table. Its atomic number is 11, and its mass number is 23. Known for its high reactivity, sodium readily reacts with air to produce sodium oxide (Na\u2082O) and with water to yield sodium hydroxide (NaOH) and hydrogen (H\u2082). These reactions are highly exothermic, resulting in the generation of substantial heat. Consequently, to mitigate its reactivity with oxygen and moisture, sodium is typically stored submerged in kerosene oil.<\/p>\n\n\n\n
<\/span>Q7. Which one of the following metals does not form amalgams? (1998)<\/strong><\/span><\/h2>\n\n\n\n(a) Zinc<\/p>\n\n\n\n
(b) Copper<\/p>\n\n\n\n
(c) Magnesium<\/p>\n\n\n\n
(d) Iron<\/p>\n\n\n\n
<\/span>Ans. (d)<\/strong><\/span><\/h3>\n\n\n\nAn amalgam constitutes an alloy comprising mercury and another metal (i.e., metal + mercury). While most metals have the capacity to form amalgams with mercury, exceptions exist. Metals such as iron, platinum, tungsten, and tantalum do not typically amalgamate with mercury.<\/p>\n\n\n\n
<\/span>Q8. Match List I (Naturally occurring substances) with List II (Elements) and select the correct answer using the codes given below the lists. (1999)<\/strong><\/span><\/h2>\n\n\n\nList I<\/strong><\/td>List II<\/strong><\/td><\/tr>A. Diamond<\/td> 1. Calcium<\/td><\/tr> B. Marble<\/td> 2. Silicon<\/td><\/tr> C. Sand<\/td> 3. Aluminium<\/td><\/tr> D. Ruby<\/td> 4. Carbon<\/td><\/tr><\/tbody><\/table><\/div><\/figure>\n\n\n\nCodes<\/strong><\/p>\n\n\n\nA B C D<\/p>\n\n\n\n
(a) 3 1 2 4<\/p>\n\n\n\n
(b) 4 2 1 3<\/p>\n\n\n\n
(c) 2 1 3 4<\/p>\n\n\n\n
(d) 4 1 2 3<\/p>\n\n\n\n
<\/span>Ans. (d)<\/strong><\/span><\/h3>\n\n\n\nThe accurate matching is A-4, B-1, C-2, D-3. Diamond, an allotrope of carbon, represents a phenomenon known as allotropy, where the same element or compound exists in two or more forms possessing similar chemical properties but differing in physical properties. Marble, composed of various constituents including lime (CaO), silica (SiO\u2082), alumina (Al\u2082O\u2083), oxides (Na\u2082O and MgO), and carbonates (MgCO\u2083 and others), predominantly contains calcium (Ca). Sand, a mixture of minerals and particles, is chiefly composed of silicon dioxide (SiO\u2082). Ruby, a pink or blood-red gemstone primarily made up of the mineral corundum or aluminum oxide (Al\u2082O\u2083), correctly identifies aluminum from the given elements<\/p>\n\n\n\n
<\/span>Q9. Cobalt-60 is commonly used in radiation therapy because it emits (1999)<\/strong><\/span><\/h2>\n\n\n\n(a) \u03b1-rays<\/p>\n\n\n\n
(b) \u03b2-rays<\/p>\n\n\n\n
(c) \u03b3-rays<\/p>\n\n\n\n
(d) X-rays<\/p>\n\n\n\n
<\/span>Ans. (c)<\/strong><\/span><\/h3>\n\n\n\nCobalt-60 finds widespread application in cancer radiation therapy due to its emission of high-intensity gamma rays (\u03b3-rays) and its comparatively extended half-life compared to other sources of gamma rays with similar intensity. As a synthetic radioactive isotope of cobalt, it possesses a half-life of 5.2714 years.<\/p>\n\n\n\n
<\/span>Q10. Consider the following statements. Glass can be etched or scratched by (1999)<\/strong><\/span><\/h2>\n\n\n\n1. diamond<\/p>\n\n\n\n
2. hydrofluoric acid<\/p>\n\n\n\n
3. aqua-regia<\/p>\n\n\n\n
4. conc. sulphuric acid<\/p>\n\n\n\n
Which of these statements are correct?<\/em><\/p>\n\n\n\n(a) 1 and 4<\/p>\n\n\n\n
(b) 2 and 3<\/p>\n\n\n\n
(c) 1 and 2<\/p>\n\n\n\n
(d) 2 and 4<\/p>\n\n\n\n
<\/span>Ans. (c)<\/strong><\/span><\/h3>\n\n\n\nStatements (1) and (2) are correct. Diamond is indeed one of the hardest substances and can be employed to cut or scratch glass. Hydrofluoric acid (HF) is utilized for writing on glass surfaces. Aqua-regia, comprising nitric acid (HNO\u2083) and hydrochloric acid (HCl) in a molar ratio of 1:3, is a potent solvent. However, aqua-regia and concentrated sulfuric acid (H\u2082SO\u2084) are generally unsuitable for etching or scratching glass due to their limited reactivity towards it.<\/p>\n\n\n\n