A doctor prescribed a tablet to a patient
Question: A doctor prescribed a tablet to a patient suffering from iron deficiency. The tablet does not look like iron. Explain. Solution: Iron is a metal but the tablet is not made up of iron metal. It is made up of a salt of iron. So, it does not look like iron....
Read More →Paheli prepared a blue coloured solution
Question: Paheli prepared a blue coloured solution of copper sulphate in beaker A and placed an iron nail in it. Boojho prepared a yellowish green solution of ferrous sulphate in beaker B and placed a copper wire in it. What changes will they observe in the two beakers after an hour? Solution: In beaker A1, a reddish brown layer of copper will deposit on the iron nail and blue coloured solution of copper sulphate will become yellowish green due to the formation of iron sulphate. This is because ...
Read More →If in figure given above,
Question: If in figure given above, iron nail is replaced by a wooden stick, will the bulb glow or not? Justify your answer. Solution: No, the bulb will not glow. It is because wood is a non-conductor of electricity....
Read More →In the given figure, you find that the bulb
Question: In the given figure, you find that the bulb glows when an iron nail is placed between two ends of wire. Complete the following sentences on the basis of this fact. (a) is a metal. (b) Metals are good of electricity. Solution: (a) Iron (b) conductors...
Read More →Find the sum of the series whose nth term is given by
Question: Find the sum of the series whose nth term is given by $\left(4 n^{3}+6 n^{2}+2 n\right)$ Solution: It is given in the question that the $\mathrm{n}^{\text {th }}$ term of the series, $a_{n}=4 n^{3}+6 n^{2}+2 n$ Now, we need to find the sum of this series, Sn. $S_{n}=\sum_{n=1}^{n} a_{n}$ $S_{n}=\sum_{n=1}^{n}\left(4 n^{3}+6 n^{2}+2 n\right)$ $=\sum_{n=1}^{n}\left(4 n^{3}\right)+\sum_{n=1}^{n}\left(6 n^{2}\right)+\sum_{n=1}^{n}(2 n)$ $=4 \sum_{n=1}^{n}\left(n^{3}\right)+6 \sum_{n=1}^{n}...
Read More →The diagonal of a square is changing at the rate
Question: The diagonal of a square is changing at the rate of $\frac{1}{2} \mathrm{~cm} / \mathrm{sec}$. Then the rate of change of area, when the area is $400 \mathrm{~cm}^{2}$, is equal to_______________ Solution: Let the side of the square be $x \mathrm{~cm}$ at any time $t$. $\therefore$ Length of the diagonal of square, $I=\sqrt{2} \times$ Side of square $=\sqrt{2} x$ $l=\sqrt{2} x$ Differentiating both sides with respect to $t$, we get $\frac{d l}{d t}=\sqrt{2} \times \frac{d x}{d t}$ It i...
Read More →Which of the following metals can displace
Question: Which of the following metals can displace the other two metals from their salt solutions? Zinc, iron, copper Solution: Zinc is most reactive among three metals and copper is least-reactive metal. Reactivity of iron is in between zinc and copper. So, zinc metal can displace the other two metals from their salt solutions....
Read More →Which liquid metal is used
Question: Which liquid metal is used for making thermometers? Solution: Mercury metal is used for making thermometers....
Read More →Why are bells made of metals?
Question: Why are bells made of metals? Solution: Metals have sonorous property. Ringing sound produce by metals is known as sonorous. So, the bells are made of metals. ....
Read More →Zinc sulphate forms a colourless
Question: Zinc sulphate forms a colourless solution in water. Will you observe any colour on adding copper turning in it? Solution: There is no colour change on adding copper turning in zinc sulphate solution because copper is less reactive than zinc and it cannot displace zinc from its salt solution. So, displacement reaction does not take place....
Read More →A purple coloured non-metal forms a brown
Question: A purple coloured non-metal forms a brown solution in alcohol which is applied on wounds as an antiseptic. Name the non-metal. Solution: Iodine is a non-metal which*.is used to make purple-coloured solution called tincture iodine which is applied on cuts and wounds as an antiseptic....
Read More →Which non-metal is used
Question: Which non-metal is used to disinfect water? Solution: Chlorine which is a non-metal, is used in water purification plants because chlorine has the ability to kill germs....
Read More →Name two majorTion:metals
Question: Name two majorTion:metals which are present in fertilisers and enhance the growth of plants Solution: Two major non-metals which are present in fertilisers and enhance the growth of plants are: . (i) Nitrogen (ii) Phosphorus...
Read More →Which non-metal is essential
Question: Which non-metal is essential for our life and all living beings inhale it during breathing? Solution: Oxygen is a non-metal which is used by plants and animals (including human beings) for breathing. Thus, oxygen (non-metal) is essential for maintaining our life....
Read More →The rate of change of the surface are of a sphere of radius r
Question: The rate of change of the surface are of a sphere of radiusrwhen the radius is increasing at the rate of 2 cm/sec is _________________. Solution: Let $r$ be the radius of sphere at any time $t$. It is given that, $\frac{d r}{d t}=2 \mathrm{~cm} / \mathrm{sec}$ Surface area of the sphere, $S=4 \pi r^{2}$ $S=4 \pi r^{2}$ Differentiating both sides with respect to $t$, we get $\frac{d S}{d t}=4 \pi \frac{d}{d t} r^{2}$ $\Rightarrow \frac{d S}{d t}=4 \pi \times 2 r \frac{d r}{d t}$ $\Right...
Read More →Name two soft metals
Question: Name two soft metals which can be cut with a knife. Solution: Metals which can easily cut with a knife (i) Sodium (ii) Potassium These are soft metals....
Read More →Find the sum of the series whose nth term is given by:
Question: Find the sum of the series whose nth term is given by: $n(n+1)(n+4)$ Solution: It is given in the question that the $n^{\text {th }}$ term of the series, $a_{n}=n(n+1)(n+4)$ Now, we need to find the sum of this series, Sn. $\mathrm{S}_{\mathrm{n}}=\sum_{\mathrm{n}=1}^{\mathrm{n}} \mathrm{a}_{\mathrm{n}}$ $\mathrm{S}_{\mathrm{n}}=\sum_{\mathrm{n}=1}^{\mathrm{n}}(\mathrm{n}(\mathrm{n}+1)(\mathrm{n}+4))$ $=\sum_{\mathrm{n}=1}^{\mathrm{n}}\left(\mathrm{n}^{3}+5 \mathrm{n}^{2}+4 \mathrm{n}\...
Read More →Which of the following property
Question: Which of the following property is not responsible for copper to be used as electrical conduction wires? (a) Ductility (b) Colour (c) Good conductor of electricity (d) It is solid Solution: (b) Colour of the copper metal is not responsible for copper to be used as electrical conduction wires....
Read More →Generally metallic oxides are basic and non-metallic
Question: Generally metallic oxides are basic and non-metallic oxides are acidic in nature. Solution of which of the following oxides in water will change the colour of blue litmus to red? (a) Sulphur dioxide (b) Iron oxide (c) Magnesium oxide (d) Copper oxide Solution: (a) Sulphur is a non-metal and it forms an acidic oxide, i.e. sulphur dioxide (S02) which turns blue litmus red....
Read More →Which of the following non-metals
Question: Which of the following non-metals reacts and catches fire on exposure to air? (a) Phosphorus (b) Nitrogen (c) Sulphur (d) Hydrogen Solution: (a) Phosphorus is a non-metal which reacts and catches fire on exposure to air....
Read More →The metal which produces hydrogen
Question: The metal which produces hydrogen gas on reaction with dilute hydrochloric acid as well as sodium hydroxide solution is (a) copper (b) iron (c) aluminium (d) sodium Solution: (c) Aluminium reacts with hydrochloric acid as well as sodium hydroxide solution to produce hydrogen gas....
Read More →Which of the following reacts
Question: Which of the following reacts with cold water vigorously? (a) Carbon (b) Sodium (c) Magnesium (d) Sulphur Solution: (b) The vigour (or intensity) of reaction of a metal with water depends on its chemical reactivity. Sodium is a very reactive metal, so it reacts violently even with cold water....
Read More →Metals generally react with dilute acids to produce hydrogen gas.
Question: Metals generally react with dilute acids to produce hydrogen gas. Which one of the following metals does not react with dilute hydrochloric acid? (a) Magnesium (b) Aluminium (c) Iron (d) Copper Solution: (d) The less reactive metals like copper, silver and gold do not react with dilute hydrochloric acid to produce hydrogen gas....
Read More →Find the sum of the series whose nth term is given by:
Question: Find the sum of the series whose nth term is given by: $\left(3 n^{2}+2 n\right)$ Solution: It is given in the question that the $\mathrm{n}^{\text {th }}$ term of the series, $a_{n}=3 n^{2}+2 n$ Now, we need to find the sum of this series, $S_{n}$. $\mathrm{S}_{\mathrm{n}}=\sum_{\mathrm{n}=1}^{\mathrm{n}} \mathrm{a}_{\mathrm{n}}$ $\mathrm{S}_{\mathrm{n}}=\sum_{\mathrm{n}=1}^{\mathrm{n}}\left(3 \mathrm{n}^{2}+2 \mathrm{n}\right)$ $=\sum_{n=1}^{n}\left(3 n^{2}\right)+\sum_{n=1}^{n}(2 n)...
Read More →The rate of change
Question: The rate of change of $\sqrt{x^{2}+16}$ with respect to $\frac{x}{x-1}$ at $x=3$ is__________________ Solution: Let $u(x)=\sqrt{x^{2}+16}$ and $v(x)=\frac{x}{x-1}$. $u(x)=\sqrt{x^{2}+16}$ Differentiating both sides with respect to $x$, we get $\frac{d u}{d x}=\frac{1}{2 \sqrt{x^{2}+16}} \times 2 x=\frac{x}{\sqrt{x^{2}+16}}$ $v(x)=\frac{x}{x-1}$ Differentiating both sides with respect to $x$, we get $\frac{d v}{d x}=\frac{(x-1) \times 1-x \times 1}{(x-1)^{2}}=-\frac{1}{(x-1)^{2}}$ Now, ...
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