Tick (✓) the correct answer
Question: Mark (✓) against the correct answer: 3 + 23x 8x2= ? (a) (1 8x)(3 +x) (b) (1 + 8x)(3 x) (c) (1 8x)(3 x) (d) none of these Solution: (b) (1 + 8x)(3 x) $3+23 x-8 x^{2}$ $=3+24 x-x-8 x^{2}$ $=3(1+8 x)-x(1+8 x)$ $=(1+8 x)(3-x)$...
Read More →Generally non-metals are not lustrous.
Question: Generally non-metals are not lustrous. Which of the following non-metals is lustrous ? (a)Sulphur (b)Phosphorus (c)Nitrogen (d)Iodine. Solution: (d).Iodine is lustrous....
Read More →Tick (✓) the correct answer
Question: Mark (✓) against the correct answer: 3 + 23x 8x2= ? (a) (1 8x)(3 +x) (b) (1 + 8x)(3 x) (c) (1 8x)(3 x) (d) none of these Solution: (b) (1 + 8x)(3 x)...
Read More →Which of the following metals are obtained
Question: Which of the following metals are obtained by electrolysis of their chlorides in molten state ? (i) Na (ii) Ca (iii) Fe (iv) Cu (a)(i) and (iv) (b)(iii) and (iv) (c)(i) and (iii) (d)(i) and (ii) Solution: (d).Both Na and Ca are obtained by the electrolysis of their molten chlorides....
Read More →Tick (✓) the correct answer
Question: Mark (✓) against the correct answer: 3 + 23x 8x2= ? (a) (1 8x)(3 +x) (b) (1 + 8x)(3 x) (c) (1 8x)(3 x) (d) none of these Solution: (b) (1 + 8x)(3 x)...
Read More →Generally, metals are solid in nature.
Question: Generally, metals are solid in nature. Which one of the following metals is found in liquid state at room temperature ? (a)Na (b)Fe (c)Al (d)Hg Solution: (d).Mercury (Hg) is a liquid at room temperature....
Read More →Mark (✓) against the correct answer:
Question: Mark (✓) against the correct answer: abab+ 1 = ? (a) (1 a)(1 b) (b) (1 a)(b 1) (c) (a 1)(b 1) (d) (a 1)(1 b) Solution: (c) (a 1)(b 1) $a b-a-b+1$ $=a(b-1)-1(b-1)$ $=(a-1)(b-1)$...
Read More →If copper is kept open in air,
Question: If copper is kept open in air, it slowly loses its shining brown surface and gains a green coating. It is due to the formation of : (a)CuSO4 (b)CUCO3CO(OH)2 (c)CU(NO3)2 (d)CuO. Solution: (b).The green coating is due to the formation of basic copper carbonate which is CuCO3.Cu(OH)2....
Read More →Stainless steel is a very useful material for our life.
Question: Stainless steel is a very useful material for our life. In stainless steel, iron is mixed with (a)Ni and Cr (b)Cu and Cr (c)Ni and Cu (d)Cu and Au. Solution: (a).is the correct answer....
Read More →5 years ago a man was 7 times as old as his son.
Question: 5 years ago a man was 7 times as old as his son. After 5 years he will be thrice as old as his son. Find their present ages. Solution: Let the present age of the son be x years and that of the father be $f$ years. 5 years back, the father was 7 times as old as his son. $\therefore(f-5)=7(x-5)$ $f=7 x-35+5$ $f=7 x-30$ ....(i) After 5 years, ages of the father and son will be $(f+5)$ and $(x+5)$, respectively. After 5 years, the father will be three times older than his son. $\therefore(...
Read More →Galvanisation is a method of protecting
Question: Galvanisation is a method of protecting iron from rusting by coating with a thin layer of (a)Chromium (b)Copper (c)Zinc (d)Tin Solution: (c).Coating the surface of iron with zinc is called galvanization....
Read More →Silver articles become black on prolonged exposure to air.
Question: Silver articles become black on prolonged exposure to air. This is due to the formation of (a)AgCN (b)Ag2O (c)Ag2S (d)Ag2S and AgCN Solution: (c).Air contains traces of hydrogen sulphide (H2S) gas which reacts with silver (Ag) to form Ag2S black in colour....
Read More →Solve this
Question: Let $R=\{(a, b): a, b, \in N$ and $ab\}$ Show that R is a binary relation on N, which is neither reflexive nor symmetric. Show that R is transitive. Solution: N is the set of all the natural numbers. N = {1, 2, 3, 4, 5, 6, 7..} $\mathrm{R}=\{(\mathrm{a}, \mathrm{b}): \mathrm{a}, \mathrm{b}, \in \mathrm{N}$ and $\mathrm{a}\mathrm{b}\}$ R = {(1, 2), (1, 3), (1, 4) . (2, 3), (2, 4), (2, 5) } For reflexivity, A relation $R$ on $N$ is said to be reflexive if $(a, a) \in R$ for all a $ N$. B...
Read More →Metals are refined by using different methods.
Question: Metals are refined by using different methods. Which of the following metals are refined by electrolytic refining ? (i) Ag (ii) Cu (iii) Na (iv) Mg (a)(i) and (ii) (b)(i) and (iii) (c)(ii) and (iii) (d)(iii) and (iv) Solution: (a).Both Ag and Cu are very hard. These are called coinage metals and are purified by electrolytic refining....
Read More →Solve the following
Question: Solve: $\frac{2 x+7}{3 x+5}=\frac{15}{17}$ Solution: $\frac{2 x+7}{3 x+5}=\frac{15}{17}$ $\Rightarrow 17(2 x+7)=15(3 x+5) \Rightarrow 34 x+119=45 x+75 \Rightarrow 119-75=45 x-34 x \Rightarrow 44=11 x \Rightarrow x=\frac{44}{11}=4 \therefore x=4$...
Read More →Which of the following metals exist in their native state in nature ?
Question: Which of the following metals exist in their native state in nature ? (i) Cu (ii) Au (iii) Zn (iv) Ag (a)(i) and (ii) (b)(ii) and (iii) (c)(ii) and (iv) (d)(iii) and (iv) Solution: (c).Both Au and Ag are very little reactive. They exist in native state. However, the metal silver may also exist in some combined states (as minerals)....
Read More →Factorise:
Question: Factorise: (i)x3 3x2+x 3 (ii) 63x2y2 7 (iii) 1 6x+ 9x2 (iv) 7x2 19x 6 Solution: (i) $x^{3}-3 x^{2}+x-3$ $=x^{2}(x-3)+1(x-3)$ $=\left(x^{2}+1\right)(x-3)$ (ii) $63 x^{2} y^{2}-7$ $=7\left(9 x^{2} y^{2}-1\right)$ $=7\left((3 x y)^{2}-(1)^{2}\right)$ [according to the formula $a^{2}-b^{2}=(a+b)(a-b)$ ] $=7(3 x y+1)(3 x y-1)$ (iii) $1-6 x+9 x^{2}$ $=9 x^{2}-6 x+1$ $=9 x^{2}-3 x-3 x+1$ $=3 x(3 x-1)-1(3 x-1)$ $=(3 x-1)(3 x-1)$ $=(3 x-1)^{2}$ $($ iv $) 7 x^{2}-19 \mathrm{x}-6$ $=7 x^{2}-21 x+...
Read More →Factorise:
Question: Factorise: (i)x3 3x2+x 3 (ii) 63x2y2 7 (iii) 1 6x+ 9x2 (iv) 7x2 19x 6 Solution: (i) $x^{3}-3 x^{2}+x-3$ $=x^{2}(x-3)+1(x-3)$ $=\left(x^{2}+1\right)(x-3)$ (ii) $63 x^{2} y^{2}-7$ $=7\left(9 x^{2} y^{2}-1\right)$ $=7\left((3 x y)^{2}-(1)^{2}\right)$ [according to the formula $a^{2}-b^{2}=(a+b)(a-b)$ ] $=7(3 x y+1)(3 x y-1)$ (iii) $1-6 x+9 x^{2}$ $=9 x^{2}-6 x+1$ $=9 x^{2}-3 x-3 x+1$ $=3 x(3 x-1)-1(3 x-1)$ $=(3 x-1)(3 x-1)$ $=(3 x-1)^{2}$ $($ iv $) 7 x^{2}-19 \mathrm{x}-6$ $=7 x^{2}-21 x+...
Read More →Which one of the following properties
Question: Which one of the following properties is not generally exhibited by ionic compounds ? (a)Solubility in water (b)Electrical conductivity in solid state (c)High melting and boiling points (d)Electrical conductivity in molten state. Solution: (b).Ionic compounds are conducting due to the movement of ions. Since the ions do not move in the solid state, these compounds are therefore, not conducting in the solid state....
Read More →Which of the following are not ionic compounds ?
Question: Which of the following are not ionic compounds ? (i) CaCl2 (ii) HCl (iii) CCl4 (iv) NaCl (a)(i) and (ii) (b)(ii) and (iii) (c)(iii) and (iv) (d)(i) and (iii) Solution: (b).Both HCl and CCl4are covalent compounds in nature....
Read More →Let A = {3, 4, 5, 6} and R = {(a, b)
Question: Let $A=\{3,4,5,6\}$ and $R=\{(a, b): a, b \in A$ and $ab$ (i) Write $\mathbf{R}$ in roster form. (ii) Find: dom (R) and range (R) (iii) Write $\mathbf{R}^{\mathbf{- 1}}$ in roster form Solution: (i) R = {(3, 4), (3, 5), (3, 6), (4, 5), (4, 6), (5, 6)} (ii) The domain of $R$ is the set of first co-ordinates of $R$ Dom(R) = {3, 4, 5} The range of $R$ is the set of second co-ordinates of $R$ Range(R) = {4, 5, 6} (iii) $R^{-1}=\{(4,3),(5,3),(6,3),(5,4),(6,4),(6,5)\}$...
Read More →Composition of aqua-regia by volume is :
Question: Composition of aqua-regia by volume is : (a)Dil HCl (3) : Cone HNO3(1) (b)Cone HCl (3) : Dil HNO3(1) (c)Cone HCl (3) : Cone HNO3(1) (d)Dil HC1 (3) : Dil HNO3(1) Solution: (c).is the correct answer....
Read More →Evaluate
Question: Evaluate {(83)2 (17)2}. Solution: {(83)2 (17)2}. $=(83+17)(83-17)$ [according to the formula $(a)^{2}-(b)^{2}=(a+b)(a-b)$ ] $=(100)(66) $=6600$...
Read More →Generally metals react with acids to give salt and hydrogen gas.
Question: Generally metals react with acids to give salt and hydrogen gas. Which of the following acids does not give hydrogen gas on reacting with metals (except Mn and Mg) ? (a)H2SO4 (b)HCl (c)HNO3 (d)All of these. Solution: (c).HNO3is a strong oxidising agent. It oxidises metals to metal oxides and then to metal nitrates and itself is reduced to either nitric oxide (NO), nitruos oxide (N2O) or nitrogen dioxide (NO2). However, both Mg and Mn evolve hydrogen on reacting with the acid....
Read More →What happens when magnesium is treated with water ?
Question: What happens when magnesium is treated with water ? (i) It does not react with water (ii) It reacts violently with water (iii) It reacts less violently with water (iv) Bubbles of hydrogen gas formed stick to the surface of the metal (a)(i) and (iv) (b)(ii) and (iii) (c)(i) and (ii) (d)(iii) and (iv) Solution: (d). (iii) Magnesium reacts with water slowly to form magnesium hydroxide along with hydrogen gas Mg(s) + 2H2O(l) - Mg(OH)2(s) + H2(g) (iv) Bubbles of hydrogen gas stick to the su...
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