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Chemical Reactions and Equations, , , , Improve your learning, , Q. 1. What is a balanced chemical equation? Why should chemical equations be, balanced? (AS1), , Answer : Balanced chemical equation: A chemical equation in which the number of, atoms of reactants and number of atoms of products is called a balanced equation., , Every chemical equation should be balanced because:, , =<According to the law of conservation of mass, atoms are neither created not destroyed, in chemical reactions., , >It means the total mass of the products formed in chemical reaction must be equal to, the mass of reactants consumed., , Q. 2 A. Balance the following chemical equations. (AS1), NaOH + H2SO4> NazSO4>H20, , Answer : NaOH + H2SO4> NazSO4>H20, , Balanced equation: 2NaOH + H2SO4>NazSO + 2H20, Explanation:, , =Step 1: Write the given unbalanced equation, , NaOH + H2SO4NazSO4 + H20., , =Step 2: Compare the number of atoms of reactants with the number of atoms of, products.

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Reactants | Products, (left side) | (right side), , , , Element | Number of | Number of, , , , , , , , , , atoms atoms, Na 1 2, o 5 5, H 3 2, Ss 1 1, , , , , , , , , , , , =>Step 3: Now, first we consider the element having unequal no. of atoms on both, sides. Thus, let us consider sodium atom. If we multiply 2 in the reactant (in NaOH), we, will get the equal number of atoms as in product (NazSOa4), , , , , , , , No. of Reactant Product (in, atoms of | (in NaOH), , sodium Na2SOs), Initially 1 2, , To 1x2=2 |2, , balance, , , , , , , , , , , , =>Step 4: Write the resulting equation:, 2NaQOH + H2SO4>Na2SO4 + H20, , =Step 5: Now check whether the equation is balanced or not by comparing the atoms, , , , , , , , , , Reactants | Products, (left side) | (right side), , Element | Number of | Number of, atoms atoms, , Na 2 2, , ° 6 5, , H 4 2, , Ss 1 al

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We find that the equation is not balanced yet. As the number of oxygen, hydrogen and, Sulphur atoms are unequal on the two sides. First balance the hydrogen number., , =>Step 6: Now, let us consider hydrogen atom. If we multiply 2 in the product (in H2O),, we will get the equal number of atoms as in reactants (in 2NaOQH and H2SOa), , , , No. of Reactants | Product (in, atoms of | (in 2NaOH | H20), hydrogen | and H2SOs), , , , , , Initially | 4 2, To 4 2x2=4, balance, , , , , , , , , , , , =Step 7: Write the resulting equation:, 2NaOH + H2SO4—>Na2SO4 + 2H20, , =Step 8: Now check whether the equation is balanced or not by comparing the atoms., , , , , , , , , , , , , , Reactants | Products, (left side) | (right side), Element | Number of | Number of, atoms atoms, Na 2 2, 0 6 6, 4 4, Ss 1 1, , , , , , , , , , , , We find that the equation is balanced now., , =Step 9: Write down the final balanced equation:, , 2NaOH + H2SO4 > Na2zSO4 + 2H20, , Q. 2 B. Balance the following chemical equations. (AS1), , Hg(NOs)2 + KI > Hgl2 + KNO3

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Answer : Hg(NOs)2 +, , KI > Hglz + KNOs, , Balanced equation: Hg(NOs)2 + 2KI > Hglz + 2KNOs, , Explanation:, , =Step 1: Write the given unbalanced equation, , g(NOsz)2 + KI > Hgl2 +, , =>Step 2: Compare th, products., , KNOs, , ie number of atoms of reactants with the number of atoms of, , , , , , , , , , , , , , , , , , , , Reactants | Products, (left side) | (right side), , Element | Number of | Number of, atoms atoms, , Hg dL. 1, , N 2 1, , 0 6 3, , K 1 1, , I 1 2, , , , , , , , =Step 3: Now, first we consider the element having unequal no. of atoms on both, sides. First, let us consider iodine atom. If we multiply 2 in the reactant (in Kl), we will, , get the equal number, , of atoms as in product (Hglz), , , , , , , , , , , , , , No. of | Reactant | Product, atoms | (in KI) (in, , of Hglz), iodine, , Initially | 1 2, , To x2= {12, balance | 2, , , , , , =>Step 4: Write the resulting equation:, , Hg(NOs)2 + 2KI > Hglz + KNO3

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=Step 5: Now check whether the equation is balanced or not by comparing the atoms, , , , , , , , , , , , , , , , Reactants | Products, (left side) | (right side), , Element | Number of | Number of, atoms atoms, , Hg 1 1, , N 2 1, , oO 6 3, , K 2 1, , I 2 2, , , , , , , , , , , , We find that the equation is not balanced yet. As the number of oxygen, nitrogen and, potassium atoms are unequal on the two sides., , First balance the potassium number., , =Step 6: Now, let us consider potassium atom. If we multiply 2 in the product (KNOs),, we will get the equal number of atoms as in reactant (in Kl), , , , , , , , No. of Reactant | Product, atoms of | (in 2KI) (in KNO3), potassium, , Initially 2 1, , To 2 1x2=2, balance, , , , , , , , , , , , =Step 7: Write the resulting equation:, Hg(NOs)2 + 2KI > Hgl2 + 2KNO3, , =Step 8: Now check whether the equation is balanced or not by comparing the atoms.