Write the balanced chemical equations
Question: Write the balanced chemical equations for the following reactions and identify the type of reaction in each case. (a) Iron (III) oxide reacts with aluminium and gives molten iron and aluminium oxide. (CBSE 2012) (b) Magnesium ribbon is burnt in an atmosphere of nitrogen gas to form solid magnesium nitride. (c) Chlorine gas is passed in an aqueous potassium iodide solution to form potassium chloride solution and solid iodine. (d) Ethanol is burnt in air to form carbon dioxide, water and...
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Question: Solve: $3 x+\frac{2}{3}=2 x+1$ Solution: $3 x+\frac{2}{3}=2 x+1$ $\Rightarrow 3 x-2 x=1-\frac{2}{3}$ $\Rightarrow x=\frac{1}{1}-\frac{2}{3}$ (L.C.M. of 1 and 3 is 3 ) $\Rightarrow x=\frac{3-2}{3}$ $\Rightarrow x=\frac{1}{3}$ $\Rightarrow x=\frac{1}{3}$ $\therefore x=\frac{1}{3}$...
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Question: Solve: $3 x+\frac{2}{3}=2 x+1$ Solution: $3 x+\frac{2}{3}=2 x+1$ $\Rightarrow 3 x-2 x=1-\frac{2}{3}$ $\Rightarrow x=\frac{1}{1}-\frac{2}{3}$ (L.C.M. of 1 and 3 is 3 ) $\Rightarrow x=\frac{3-2}{3}$ $\Rightarrow x=\frac{1}{3}$ $\Rightarrow x=\frac{1}{3}$ $\therefore x=\frac{1}{3}$...
Read More →Write the balanced chemical equations for
Question: Write the balanced chemical equations for the following reactions and identify the type of reaction in each (a) Nitrogen gas is treated with hydrogen gas in the presence of a catalyst at 773 K to form ammonia gas. (b) Potassium hydroxide solution is treated with acetic acid to form potassium acetate and water. (c) Ethanol is warmed with ethanoic acid to form ethyl acetate in the presence of concentrated H2SO4. (d) Ethene is burnt in the presence of oxygen to form carbon dioxide, water ...
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Question: Solve: $\frac{7 y}{5}=y-4$ Solution: $\frac{7 y}{5}=y-4$ By cross multiplication: $\Rightarrow 7 y=5(y-4)$ $\Rightarrow 7 y=5 y-20$ $\Rightarrow 7 y-5 y=-20$ $\Rightarrow 2 y=-20$ $\Rightarrow y=\frac{-20}{2}=-10$ $\therefore y=-10$...
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Question: If $y=\frac{e^{x}-e^{-x}}{e^{x}+e^{-x}}$, prove that $\frac{d y}{d x}=1-y^{2}$ Solution: Given $y=\frac{e^{x}-e^{-x}}{e^{x}+e^{-x}}$ On differentiating $y$ with respect to $x$, we get $\frac{d y}{d x}=\frac{d}{d x}\left(\frac{e^{x}-e^{-x}}{e^{x}+e^{-x}}\right)$ Recall that $\left(\frac{\mathrm{u}}{\mathrm{v}}\right)^{\prime}=\frac{\mathrm{vu}^{\prime}-\mathrm{uv}^{\prime}}{\mathrm{v}^{2}}$ (quotient rule) $\Rightarrow \frac{d y}{d x}=\frac{\left(e^{x}+e^{-x}\right) \frac{d}{d x}\left(e...
Read More →Which of the following are combination reactions ?
Question: Which of the following are combination reactions ? (i) 2KClO3 - 2KCl + 3O (ii) MgO + H2O Mg(OH)2 (iii) 4Al + 3O2 2Al2O3 (iv) Zn + FeSO4- ZnSO4+ Fe (a)(i) and (iii) (b)(iii) and (iv) (c)(ii) and (iv) (d)(ii) and (iii). Solution: (d).Both the reactions (ii) and (iii) are the examples of combination reactions....
Read More →Solve: 9x + 5 = 4(x − 2) + 8
Question: Solve:9x+ 5 = 4(x 2) + 8 Solution: $9 x+5=4(x-2)+8$ $\Rightarrow 9 x+5=4 x-8+8$ $\Rightarrow 9 x+5=4 x$ $\Rightarrow 9 x-4 x=-5$ $\Rightarrow 5 x=-5$ $\Rightarrow x=\frac{-5}{5}=-1$ $\therefore x=-1$...
Read More →In which of the following chemical equations,
Question: In which of the following chemical equations, the abbreviations represent the correct states of the reactants and products involved at reaction temperature ? (a)H2(l) + O2(l) 2H2O(g) (b)H2(g) + O2(l) 2H2O(l) (c)2H2(g) + O2(g) 2H2O(l) (d)2H2(0) + O2(g) 2H2O(g) Solution: (d).The reaction is carried upon strong heating. At this temperature, H2O formed is in gaseous state....
Read More →Solve: 2z − 1 = 14 − z
Question: Solve:2z 1 = 14 z Solution: $2 z-1=14-z$ $\Rightarrow 2 z+z=14+1$ $\Rightarrow 3 z=15$ $\Rightarrow z=\frac{15}{3}=5$ $\therefore z=5$...
Read More →Which one of the following processes involve chemical reactions ?
Question: Which one of the following processes involve chemical reactions ? (a)Storing of oxygen gas under pressure in a gas cylinder (b)Liquefaction of air (c)Keeping petrol in a china dish in the open (d)Heating copper wire in the presence of air at high temperature. Solution: (d).Copper will react with oxygen present in air upon strong heating to form copper (II) oxide or cupric oxide....
Read More →Solve: 5x + 7 = 2x − 8
Question: Solve: 5x + 7 = 2x 8 Solution: $5 x+7=2 x-8$ $\Rightarrow 5 x-2 x=-8-7$ $\Rightarrow 3 x=-15$ $\Rightarrow x=\frac{-15}{3}=-5$ $\therefore x=-5$...
Read More →Solve: 8x + 3 = 27 + 2x
Question: Solve: 8x + 3 = 27 + 2x Solution: $8 x+3=27+2 x$ $\Rightarrow 8 \mathrm{x}-2 \mathrm{x}=27-3$ $\Rightarrow 6 \mathrm{x}=24$ $\Rightarrow \mathrm{x}=\frac{24}{6}=4$ $\therefore \mathrm{x}=4$...
Read More →The following reaction is used for
Question: The following reaction is used for the preparation of oxygen gas in the laboratory Which of the following statement(s) is(are) correct about the reaction ? (a)It is a decomposition reaction and is endothermic in nature (b)It is a combination reaction (c)It is a decomposition reaction and is accompanied by release of heat (d)It is a photochemical decomposition reaction and exothermic in nature Solution: (a) It is a decomposition reaction and is endothermic in nature...
Read More →Which of the following gases can
Question: Which of the following gases can be used for storage of fresh sample of an oil for a long time ? (a)Carbon dioxide or oxygen (b)Nitrogen or oxygen (c)Carbon dioxide or helium (d)Helium or nitrogen. Solution: (d).Both helium (He) and nitrogen (N2) can be used. In their presence, rancidity of fresh sample of an oil will not take place....
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Question: If $\mathrm{y}=\frac{\mathrm{x} \sin ^{-1} \mathrm{x}}{\sqrt{1-\mathrm{x}^{2}}}$, prove that $\left(1-\mathrm{x}^{2}\right) \frac{\mathrm{dy}}{\mathrm{dx}}=\mathrm{x}+\frac{\mathrm{y}}{\mathrm{x}}$. Solution: Given $y=\frac{x \sin ^{-1} x}{\sqrt{1-x^{2}}}$ On differentiating $y$ with respect to $x$, we get $\frac{d y}{d x}=\frac{d}{d x}\left(\frac{x \sin ^{-1} x}{\sqrt{1-x^{2}}}\right)$ Recall that $\left(\frac{\mathrm{u}}{\mathrm{v}}\right)^{\prime}=\frac{\mathrm{vu}^{\prime}-\mathrm{...
Read More →In the double displacement reaction between
Question: In the double displacement reaction between aqueous potassium iodide .and aqueous lead nitrate, a yellow precipitate of lead iodide is formed. While performing the activity if lead nitrate is not available, which of the following can be used in place of lead nitrate ? (a)Lead sulphate (insoluble) (b)Lead acetate (c)Ammonium nitrate (d)Potassium sulphate. Solution: (b).Lead sulphate being insoluble in water will not react. However, lead acetate can be used since it is water soluble in n...
Read More →Which of the following is(are) an endothermic process (es) ?
Question: Which of the following is(are) an endothermic process (es) ? (i) Dilution of sulphuric acid (ii) Sublimation of dry ice (iii) Condensation of water vapours (iv) Evaporation of water (a)(i) and (iii) (b)(ii) only (c)(iii) only (d)(ii) and (iv) Solution: (d).Both sublimation of dry ice (ii) and evaporation of water (iv) are of endothermic nature....
Read More →Electrolysis of water is a decomposition reaction.
Question: Electrolysis of water is a decomposition reaction. The mole ratio of hydrogen and oxygen gases liberated during electrolysis of water is (a)1:1 (b)2:1 (c)4:1 (d)1:2. Solution: (b)2:1...
Read More →Barium chloride on reacting with ammonium sulphate
Question: Barium chloride on reacting with ammonium sulphate forms barium sulphate and ammonium chloride. Which of the following correctly represents the type of the reaction involved ? (i) Displacement reaction (ii) Precipitation reaction (iii) Combination reaction (iv) Double displacement reaction (a)(i) only (b)(ii) only (c)(iv) only (d) (ii) and (iv) Solution: (d).A white precipitate of BaSO4is formed. The reaction is double displacement in nature....
Read More →Solid calcium oxide reacts vigorously
Question: Solid calcium oxide reacts vigorously with water to form calcium hydroxide accompanied by liberation of heat. This process is called slaking of lime. Calcium hydroxide dissolves in water to form a solution called lime water. Which among the following is (are) true about slaking of lime and the solution formed ? (i) It is an endothermic reaction (ii) It is an exothermic reaction (iii) The pH of the resulting solution will be more than seven (iv) The pH of the resulting solution will be ...
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Question: Tick (✓) the correct answer: 3 + 23y 8y2= ? (a) (1 8y)(3 +y) (b) (1 + 8y)(3 y) (c) (1 8y)(y 3) (d) (8y 1)(y+ 3) Solution: (b) (1 + 8y)(3 y) $3+23 y-8 y^{2}$ $=3+24 y-y-8 y^{2}$ $=3(1+8 y)-y(1+8 y)$ $=(3-y)(1+8 y)$...
Read More →Which among the following statement(s) is(are) true ?
Question: Which among the following statement(s) is(are) true ? Exposure of silver chloride to sunlight for a long duration turns grey due to (i) the formation of silver by decomposition of silver chloride (ii) sublimation of silver chloride (iii) decomposition of chlorine gas from silver chloride (iv) oxidation of silver chloride (a)(i) only (b)(i) and (iii) (c)(ii) and (iii) (d)(iv) only Solution: (a).Silver chloride is sensitive to sun light and decomposes slowly to give silver which is grey ...
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Question: If $\mathrm{y}=\sqrt{\mathrm{x}}+\frac{1}{\sqrt{\mathrm{x}}}$, prove that $2 \mathrm{x} \frac{\mathrm{dy}}{\mathrm{dx}}=\sqrt{\mathrm{x}}-\frac{1}{\sqrt{\mathrm{x}}}$. Solution: Given $y=\sqrt{x}+\frac{1}{\sqrt{x}}$ On differentiating $y$ with respect to $x$, we get $\frac{\mathrm{dy}}{\mathrm{dx}}=\frac{\mathrm{d}}{\mathrm{dx}}\left(\sqrt{\mathrm{x}}+\frac{1}{\sqrt{\mathrm{x}}}\right)$ $\Rightarrow \frac{\mathrm{dy}}{\mathrm{dx}}=\frac{\mathrm{d}}{\mathrm{dx}}(\sqrt{\mathrm{x}})+\frac...
Read More →Tick (✓) the correct answer
Question: Tick (✓) the correct answer: 4z2 8z+ 3 = ? (a) (2z 1)(2z 3) (b) (2z+ 1)(3 2z) (c) (2z+ 3)(3z 1) (c) (z 1)(4z 3) Solution: (a) (2z 1)(2z 3) $4 z^{2}-8 z+3$ $=4 z^{2}-6 z-2 z+3$ $=2 z(2 z-3)-1(2 z-3)$ $=(2 z-1)(2 z-3)$...
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