10th
- Why does an aqueous solution of an acid conduct electricity? The presence of hydrogen (H⁺) or hydronium (H₃O⁺) ions in the aqueous solution of an acid are responsible for conducting electricity. 1
- Why do HCl, HNO3, etc., show acidic characters in aqueous solutions while solutions of compounds When HCl or HNO₃ are mixed with water then they dissolve in water to form H⁺ or H₃O⁺ ions which shows their acidic character. For example ju... 1
- Metal compound A reacts with dilute hydrochloric acid to produce effervescence. CaCO₃ (s) + 2HCl (aq) → CaCl₂ (aq) + CO₂ (g) + H₂O (l) Calcium Carbonate + Hydrochloric acid → Calcium Chloride + Carbon dioxide + Water 1
- Which gas is usually liberated when an acid reacts with a metal? Hydrogen gas is usually liberated when an acid reacts with a metal For example: When zinc granules react with dilute sulphuric acid, then hy... 1
- Why should curd and sour substances not be kept in brass and copper vessels? Curd and other sour substances contain acids. Therefore, when they are kept in brass and copper vessels, the metal reacts with the acid to l... 2
- You have been provided with three test tubes. One of them contains distilled water Answer: Use red litmus to find the base first, then use the blue litmus obtained from it to find the acid; the remaining tube is distilled w... 1
- Explain the following terms with one example each. (a) Corrosion (b) Rancidity Corrosion is defined as a process where materials, usually metals, deteriorate as a result of a chemical reaction with air, moisture, chemic... 1
- Oil and fat containing food items are flushed with nitrogen. Why? Oil and fat containing food items flushed with nitrogen because nitrogen acts as an antioxidant and it prevents them from being oxidised 2
- Why do we apply paint on iron articles? Iron articles are painted because it prevents them from rusting. When painted, the contact of iron articles from moisture and air is cut off... 1
- A shiny brown-coloured element ‘X’ on heating in air becomes black in colour. Element 'X' is copper and the black coloured compound is copper (11) oxide Equation: 2Cu_((s)) + O_(2(g) )→ 2CuO_((s)) 1
- Explain the following in terms of gain or loss of oxygen with two examples each. Oxidation: Addition of oxygen or electronegative element to a atom, molecule, or ion or removal of hydrogen or electropositive element from... 1
- What do you mean by a precipitation reaction? Explain by giving examples. A reaction in which an insoluble solid (called precipitate) is formed is called a precipitation reaction.For Example: Na₂CO₃ (aq) + CaCl₂ (a... 1
- In the refining of silver, the recovery of silver from silver nitrate solution involved displacement 2AgNO₃ (aq) + Cu (s) → Cu(NO₃)₂ (aq) + 2Ag (s) Silver Nitrate + Copper → Copper Nitrate + Silver 1
- What is the difference between displacement and double displacement reactions? In a displacement reaction, a more reactive element replaces a less reactive element from a compound. For Example: CuSo₄ (aq) + Zn (s) → ZnS... 1
- Write one equation each for decomposition reactions where energy is supplied Thermal decomposition : read the image for answer https://lh3.googleusercontent.com/-CpMGoV1AuvA/Ya3V5xIPrnI/AAAAAAAAC3I/6WMqQz11TQc2TSOK9X6... 2
- Why are decomposition reactions called the opposite of combination reactions? Decomposition reactions are those in which a compound breaks down to form two or more substances. These reactions require a source of energy... 1
- Why is respiration considered an exothermic reaction? Explain. Respiration is considered as an exothermic reaction because in respiration oxidation of glucose takes place which produces large amount of h... 1
- What does one mean by exothermic and endothermic reactions? Give examples. Exothermic reaction:: Reactions in which heat is released along with the formation of products are called exothermic chemical reactions. Eg:... 1
- Write the balanced chemical equation for the following and identify the type of reaction in each case. (a) 2KBr (aq) + BaI₂ (aq) → 2KI (aq) + BaBr₂ (s): Double displacement reaction (b) ZnCO₃ (s) → ZnO (s) + CO₂ (g): Decomposition reaction (c)... 1
- Write the balanced chemical equations for the following reactions. (a) Calcium hydroxide (a) Ca(OH)₂ + CO₂ → CaCO₃ + H₂O (b) Zn + 2AgNO₃ → Zn(NO₃)₂ + 2Ag (c) 2Al + 3CuCl₂ → 2AlCl₃ + 3Cu (d) BaCl2 + K₂SO₄ → BaSO₄ + 2KCl 1
- Balance the following chemical equations. (i) HNO3 + Ca(OH)2 → Ca(NO3)2 + H2O (i) 2HNO₃ + Ca(OH)₂ → Ca(NO₃)₂ + 2H₂O (ii) 2NaOH + H₂SO₄ → Na₂SO₄ + 2H₂O (iii) NaCl + AgNO₃ → AgCl + NaNO₃ (iv) BaCl₂ + H₂SO₄ → BaSO₄ + 2HCl 1
- Translate the following statements into chemical equations and then balance them. (a) 3H₂ (g) + N₂ (g) → 2NH₃ (g) (b) 2H₂S (g) + 3O₂ (g) → 2H₂O (l) + 2SO₂ (g) (c) 3BaCl₂ (aq) + Al₂(SO₄)₃ (aq) → 2AlCl₃ (aq) + 3BaSO₄ (s) (d)... 1
- What is a balanced chemical equation? Why should chemical equations be balanced? A reaction which has an equal number of atoms of all the elements on both sides of the chemical equation is called a balanced chemical equat... 1
- What happens when dilute hydrochloric acid is added to iron filings? Tick the correct answer. Correct option is a) Hydrogen gas and iron chloride are produced. 1