Chemistry Location

Elements can be classified as metals, non-metals and metalloids on the basis of their physical and chemical properties.  Physical properties of metals: Lustre : Metals in their pure state have a shining surface called metallic lustre. Malleability : Metals are malleable i.e can be beaten into thin sheets. Note : Gold and silver are the most malleable metals. Ductility : The ability of metals to be drawn into thin wires is called ductility.  • Gold is the most ductile metal.  Note : 1 gramof gold can be drawn into a thin wire about 2km long because of their malleability and ductility. Conductivity : Metals are good conductors of heat and electricity • Silver and copper are good (best) conductors of heat and electricity.  • Lead and mercury are comparatively poor conductors of heat and electricity.  Sonorous : Metals are sonorous i.e they produce a sound when hit (strike) with a hard surface (object). • The metals that produce a sound on striking a hard surface are said to be sonorous. 

Acid :  The chemical substance which are sour in taste , change the colour of blue litmus to red and gives H+ ion in aqueous solution is called acid. There are two types of acids: 1.Strong acids :  An acid which is completely (100%) ionised in water and produces (give rise) large amount (more number) of hydrogen ions (H+ ions) is called a strong acid. Example : Hydrochloric acid (HCl), sulphuric acid (H₂SO₄), nitric acid (HNO₃ ). 2.Weak acids : An acid which is partially (<100%) ionised (do not dissociate completely i.e incomplete ionised) in water and produces (give rise) small amount (number) of hydrogen ions (H+ ions) is called a weak acid. Example : Acetic acid or Ethanoic acid (CH₃COOH), formic acid (HCOOH), Carbonic acid (H₂CO₃), sulphurous acid (H₂SO₃), citric acid, tartaric acid etc. Base : The chemical substance which are bitter in taste , soapy to touch, change the colour of the red litmus to blue and gives OH- ion in aqueous solut

Que : MnO₂ + xHCl → MnCl₂ + yH₂O + zCl₂ In order to balance the above chemical equation, the values of x, y and z respectively are: (a) 6, 2, 2               (b) 4, 1, 2                  (1Marks) (c) 4, 2, 1                 (d) 2, 2, 1                    (2023)  Ans:   Que: Calcium oxide reacts vigorously with water to produce slaked lime. CaO (s) + H₂O → Ca(OH)₂ (aq) This reaction can be classified as: (A) Combination reaction      (B) Exothermic reaction (C) Endothermic reaction                 (1 Marks) (D) Oxidation reaction                         (2020) Which of the following is a correct option? (i) (A) and (C)                     (ii) (C) and (D)   (iii) (A), (C) and (D)           (iv) (A) and (B)     Ans: Que: 2 g of ferrous sulphate crystals are heated in a dry boiling tube.              (3 Marks), (2019) (a) List any two observations. (b) Name the type of chemical reaction taking place. (c) Write balanced chemical equation for the reaction and name the products formed. Ans:

• Whenever a chemical change occurs, we can say that a chemical reaction takes place i.e Chemical reactions involve chemical changes. Chemical Change :   • If the identity, composition or nature of a chemical substance change and can not be reserved by any physical process, it is called chemical change . Chemical Reaction :   • The process involving a chemical change is called chemical reaction . • The process in which one or more substance as reactants gets converted (transformed) into new substances with new properties in product as a result of chemical change is called chemical reaction . Reactants :   • The substances that undergo chemical change or takes part in a chemical reaction is called reactants .  Products :   • The new substances produced (formed) during the reaction as a result of chemical change are called products . • Chemical reactions involves the breaking and making of bonds between atoms i.e in a chemical reaction old bonds are broken to form a new bond