Science
- If 0.2 mol of the following substances are required how many grams of those substances should be taken? (i) We know that, Molar mass= sum of constituent atomic masses Molar mass of NaCl= 23 + 35.5 = 58.5 g/mol Number of moles of a substance= Mo... 1
- Deduce the number of molecules of the following compounds in the given quantities. (i) 32g oxygen, (ii) 90g water (i) 32 g of oxygen : Molecular mass of O_(2 )= 2x16=32 Number of moles of O_(2 )= Mass of O₂ in grams/Molecular mass of O_(2 )= 32/32 = 1mol... 1
- Two samples ‘m’ and ‘n’ of slaked lime were obtained from two different reactions. The details about their composition Slaked lime have two samples ‘m’ and ‘n’ Sample m Mass :7g Mass of constituent oxygen :2g Mass of constituent calcium :5g In sample m, the r... 1
- Write the names of the following compounds and deduce their molecular masses. (i) Na₂SO_(4 )- Sodium sulphate. Molecular mass= sum of masses of individual components Atomic mass of, Na = 23u, S=32u, O=16u ∴ Molecular m... 1
- Explain with examples what is meant by a 'mole' of a substance. A mole is that quantity of a substance whose mass in grams is equal in magnitude to the molecular mass of that substance in daltons. The SI... 1
- What is meant by Unified Atomic Mass Instead of relative atomic mass, it is now possible to determine atomic masses in kg. The Unified Atomic Mass Unit or Dalton is a standard u... 2
- Explain the need for a reference atom for atomic mass. Give some information about two reference atoms. Since the atom is very very small it is very difficult to determine its mass very accurately, Hence the concept of the relative mass was As... 1
- M is a bivalent metal. Write down the steps to find the chemical formulae of its compounds formed with the radicals, M is a bivalent metal that is : M²⁺ Step 1 : Write the symbols and valencies of of M and sulphate. Symbols M SO₄ Valency 2 2 Step 2 : Cross-... 1
- Explain how the element sodium is monovalent. Sodium is a metal which has atomic number 11. It has 1 electron in its last shell which means it has 1 valence electron. In order to get sta... 1
- Write the steps in deducing the chemical formulae of the following compounds. (v) Aluminium hydroxide Aluminium hydroxide : Step 1 : Write the symbols and valencies of the radicals. Symbols Al OH Valency 3 1 Step 2 : Cross-multiply symbols of... 1
- Write the steps in deducing the chemical formulae of the following compounds. (iv) Calcium oxide Calcium oxide : Step 1 : Write the symbols and valencies of the radicals. Symbols Ca O Valency 2 2 Step 2 : Cross-multiply symbols of radica... 1
- Write the steps in deducing the chemical formulae of the following compounds. (iii) Ferric phosphate Ferric phosphate : Step 1 : Write the symbols and valencies of the radicals. Symbols Fe PO₄ Valency 3 3 Step 2 : Cross-multiply symbols of r... 1
- Write the steps in deducing the chemical formulae of the following compounds. (ii) Potassium nitrate, Potassium nitrate : Step 1 : Write the symbols and valencies of the radicals. Symbols K NO₃ Valency 1 1 Step 2 : Cross-multiply symbols of r... 1
- Write the steps in deducing the chemical formulae of the following compounds. Sodium sulphate Sodium sulphate : Step 1 : Write the symbols and valencies of the radicals. Symbols Na SO₄ Valency 1 2 Step 2 : Cross-multiply symbols of ra... 1
- Write symbols of the following elements and the radicals obtained from them and indicate the charge on the radicals. Element Symbols Charge 1. Mercury Hg Mercurous- Hg⁺ 2. Potassium K Potassium- K⁺ 3. Nitrogen N Azide- N₃⁻ 4. Copper Cu Cuprous- Cu⁺ 5. Sulph... 2
- Give example Trivalent basic radicals Trivalent Basic Radical : (i) Al^(3+ ) (ii) Cr³⁺ (iii) Fe³⁺ (iv) Au³⁺ 1
- give example Bivalent acidic radicals Bivalent Acidic Radical : (i) S^(2- ) (ii) O^(2- ) (iii) Se^(2- ) 2
- Give example Metals with variable valency Metal With Variable Valency : (i) Cu → Cu^(+ )Cu²⁺, (ii) Hg → Hg⁺, Hg²⁺ (iii) Fe → Fe²⁺ , Fe³⁺ 1
- Give example Composite radicals Composite Radical : (i) SO₄^( 2- ) (ii) H₃O⁺ (iii) NH₄^(+ ) (iv) HCO₃^(- ) (v) SO₄^(2- ) (vi) NO₄⁻ 2
- Give examples Basic radicals Basic Radical : (i) Na⁺ (ii) Fe²⁺ (iii) Ag⁺ (iv)^( )Al³⁺ (v) Cr³⁺ (vi) Sn²⁺ 2
- Give examples. Positive ions Positive ions : (i) Sodium Ions Na⁺ (ii) Silver ions Ag⁺ (iii) Aluminium ions^( )Al^(3+ ), (iv) Chromium ion Cr³⁺ (v) Calcium ion Ca²⁺ 1
- Why are fuse wires used? Used to protect domestic appliances, fuse wire has specific melting point and is made of a mixture of substances. It is connected in series... 1
- Explain Ohm’s law with the formula. George Simon Ohm, a German Scientist put across a law known as Ohm’s law, from which the relationship between the current flowing through a... 1
- What are free electrons? Free electrons are the one or more outer shell electrons found in every atom of a metallic conductor, which are bound weakly to the nucleus.... 1