9th
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- Formation of sodium chloride from sodium and chlorine. Atomic number of Sodium (Na) atom is 11. Electronic configuration is: Na = 2, 8, 1 So it contains 1 valence electron. In order to achieve th... 1
- Classify the following oxides into three types and name the types. CaO, MgO, CO2 , SO3 , Na2O, ZnO, Al2O3 , Fe2O3 1) Acidic Oxides: CO₂ (Carbon dioxide), SO₃ (Sulfur trioxide) 2) Basic Oxides: CaO (Calcium oxide), MgO (Magnesium oxide), Na₂O (Sodium oxid... 1
- Dilute H2SO4 was taken in an electrolytic cell and electric current was passed through it. When a dilute solution of sulfuric acid is electrolysed, gases are produced at both the anode and the cathode electrode. The gas produced at... 1
- Pieces of blue vitriol were heated in a test tube. On cooling, water was added to it. When pieces of blue vitriol are heated in a test tube, then crystal structure of blue vitriol broke down to form a colourless powder and wat... 1
- Dilute HCl was added to limestone. Limestone is calcium carbonate. When Dilute HCl was added to limestone, it forms calcium chloride, water and carbon dioxide gas. 2HCl + CaCO... 1
- Zinc oxide was added to dilute HCl and zinc oxide was added to dilute NaOH. When Zinc oxide is added to dilute HCl, it forms zinc chloride and water and neutralization reaction takes place. In this reaction zinc oxid... 1
- Magnesium oxide was added to dilute HCl and magnesium oxide was a added to dilute NaOH. Bases react only with oxides of non-metal to form salt and water and neutralization reaction take place. Magnesium oxide is a base. When Mag... 2
- A litmus paper was dropped into 2ml dilute HCl. Then 2ml concentrated NaOH was added to it and stirred. When litmus paper is dipped into 2 mL of dilute HCl solution , then blue litmus paper is turned into red colour and there is no effect on re... 1
- Two or three filings of copper were added to 10ml dilute nitric acid and stirred. Answer: Copper dissolves slowly, the solution turns blue (copper nitrate forms), and a colourless gas, nitric oxide (NO), is given off, whic... 1
- Two drops of the indicator phenolphthalein were added to 10ml solution of sodium hydroxide. When two drops of Phenolphthalein indicator are added to 10 mL solution of Sodium hydroxide, then the solution turns light pink in colour be... 1
- 50ml water is added to 50ml solution of copper sulphate. Write down the changes that will be seen in each Answer: The blue colour of the solution becomes lighter (paler); no chemical reaction takes place. Copper sulphate solution is blue because... 1
- Identify the odd one out and justify. (a) Chloride, nitrate, hydride, ammonium (a) Chloride, nitrate, hydride, ammonium Answer Ammonium - Ammonium is odd because Ammonium is cation and rest are anions. (b) Hydrogen chlo... 1
- 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