The diameter of a metallic ball is 4.2 cm.
[question] Question. The diameter of a metallic ball is $4.2 \mathrm{~cm}$. What is the mass of the ball, if the density of the metal is $8.9 \mathrm{~g}$ per $\mathrm{cm}^{3} ?\left[\right.$ Assume $\left.\pi=\frac{22}{7}\right]$ [/question] [solution] Solution: Radius $(r)$ of metallic ball $=\left(\frac{4.2}{2}\right) \mathrm{cm}=2.1 \mathrm{~cm}$ Volume of metallic ball $=\frac{4}{3} \pi r^{3}$ $=\left[\frac{4}{3} \times \frac{22}{7} \times(2.1)^{3}\right] \mathrm{cm}^{3}$ $=38.808 \mathrm{~...
Read More →Write the balanced chemical equation for the following and
[question] Question. Write the balanced chemical equation for the following and identify the type of reaction in each case. (a) Potassium bromide(aq) $+$ Barium iodide(aq) $\rightarrow$ Potassium iodide(aq) $+$ Barium bromide(s) (b) Zinc carbonate(s) $\rightarrow$ Zinc oxide(s) + Carbon dioxide(g) (c) Hydrogen $(\mathrm{g})+$ Chlorine $(\mathrm{g}) \rightarrow$ Hydrogen chloride $(\mathrm{g})$ (d) Magnesium(s) + Hydrochloric acid(aq) $\rightarrow$ Magnesium chloride(aq) $+$ Hydrogen(g) [/questio...
Read More →Why are we able to sip hot tea or milk
[question] Question. Why are we able to sip hot tea or milk faster from a saucer rather than a cup? [/question] [solution] Solution: Tea in a saucer has larger surface area than in a cup. The rate of evaporation is faster with increased surface area. The cooling of tea in saucer takes place sooner than in a cup. Hence we are able to sip hot tea or milk faster from a saucer rather than a cup. [/solution]...
Read More →Why does our palm feel cold when we put
[question] Question. Why does our palm feel cold when we put some acetone or petrol or perfume on it? [/question] [solution] Solution: Acetone, petrol or perfume evaporate when they come into contact with air. The evaporation causes cooling sensation in our hands. [/solution]...
Read More →Write the balanced chemical equations for the following reactions.
[question] Question. Write the balanced chemical equations for the following reactions. (a) Calcium hydroxide $+$ Carbon dioxide $\rightarrow$ Calcium carbonate $+$ Water (b) Zinc $+$ Silver nitrate $\rightarrow$ Zinc nitrate $+$ Silver (c) Aluminium $+$ Copper chloride $\rightarrow$ Aluminium chloride $+$ Copper (d) Barium chloride $+$ Potassium sulphate $\rightarrow$ Barium sulphate $+$ Potassium chloride [/question] [solution] solution: (a) $\mathrm{Ca}(\mathrm{OH})_{2}+\mathrm{CO}_{2} \right...
Read More →How does the water kept in an earthen pot
[question] Question. How does the water kept in an earthen pot (matka) become cool during summer? [/question] [solution] Solution: The earthen pot is porous with lot of pores on it, the water oozes out through these pores and the water gets evaporated at the surface of the pot thereby causing cooling effect. This makes the pot cold and the water inside the pot cools by this process. [/solution]...
Read More →Balance the following chemical equations.
[question] Question. Balance the following chemical equations. (a) $\mathrm{HNO}_{3}+\mathrm{Ca}(\mathrm{OH})_{2} \rightarrow \mathrm{Ca}\left(\mathrm{NO}_{3}\right)_{2}+\mathrm{H}_{2} \mathrm{O}$ (b) $\mathrm{NaOH}+\mathrm{H}_{2} \mathrm{SO}_{4} \rightarrow \mathrm{Na}_{2} \mathrm{SO}_{4}+\mathrm{H}_{2} \mathrm{O}$ (c) $\mathrm{NaCl}+\mathrm{AgNO}_{3} \rightarrow \mathrm{AgCl}+\mathrm{NaNO}_{3}$ (d) $\mathrm{BaCl}_{2}+\mathrm{H}_{2} \mathrm{SO}_{4} \rightarrow \mathrm{BaSO}_{4}+\mathrm{HCl}$ [/...
Read More →Why does a desert cooler cool better on a hot dry day?
[question] Question. Why does a desert cooler cool better on a hot dry day? [/question] [solution] Solution: The outer walls of the cooler get sprinkled by water constantly. This water evaporates due to hot dry weather. Evaporation causes cooling of inside air of cooler. This cool air is sent in the room by the fan. [/solution]...
Read More →Translate the following statements into
[question] Question. Translate the following statements into chemical equations and then balance them. (a) Hydrogen gas combines with nitrogen to form ammonia. (b) Hydrogen sulphide gas burns in air to give water and sulphur dioxide. (c) Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate. (d) Potassium metal reacts with water to give potassium hydroxide and hydrogen gas. [/question] [solution] solution: (a) $3 \mathrm{H}_{2}(\mathrm{~g}...
Read More →Suggest a method to liquefy atmospheric gases?
[question] Question. Suggest a method to liquefy atmospheric gases? [/question] [solution] Solution: The atmospheric gases are taken in a cylinder with piston fitted on it. By cooling and applying pressure on them, the gases can be liquefied. [/solution]...
Read More →What is a balanced chemical equation ?
[question] Question. What is a balanced chemical equation ? Why should chemical equations be balanced ? [/question] [solution] solution: A reaction which has an equal number of atoms of all the elements on both sides of the chemical equation is called a balanced chemical equation. The law of conservation of mass states that mass can neither be created nor destroyed. Hence, in a chemical reaction, the total mass of reactants should be equal to the total mass of the products. It means that the tot...
Read More →For any substance,
[question] Question. For any substance, why does the temperature remain constant during the change of state? [/question] [solution] Solution: During the change of state of any matter heat is supplied to the substance. The molecules of this matter use heat to overcome the force of attraction between the particles, at this period of time, temperature remains constant. This extra heat is acquired by the molecules in the form of hidden heat called latent heat to change from one state of matter to th...
Read More →Find the volume of a sphere whose radius is
[question] Question. Find the volume of a sphere whose radius is (i) $7 \mathrm{~cm}$ (ii) $0.63 \mathrm{~m}$ $\left[\right.$ Assume $\left.\pi=\frac{22}{7}\right]$ [/question] [solution] Solution: (i) Radius of sphere $=7 \mathrm{~cm}$ Volume of sphere $=\frac{4}{3} \pi r^{3}$ $=\left[\frac{4}{3} \times \frac{22}{7} \times(7)^{3}\right] \mathrm{cm}^{3}$ $=\left(\frac{4312}{3}\right) \mathrm{cm}^{3}$ $=1437 \frac{1}{3} \mathrm{~cm}^{3}$ Therefore, the volume of the sphere is $1437 \frac{1}{3} \m...
Read More →What happens when dilute hydrochloric acid is added to iron filings?
[question] Question. What happens when dilute hydrochloric acid is added to iron filings? Tick the correct answer. (a) Hydrogen gas and iron chloride are produced. (b) Chlorine gas and iron hydroxide are produced. (c) No reaction takes place. (d) Iron salt and water are produced. [/question] [solution] solution: (a) Hydrogen gas and iron chloride are produced.The reaction is as follows: $\mathrm{Fe}(\mathrm{s})+2 \mathrm{HCl}(\mathrm{aq}) \rightarrow \mathrm{FeCl}_{2}(\mathrm{aq})+\mathrm{H}_{2}...
Read More →What is the physical state of water at :
[question] Question. What is the physical state of water at : (a) 250°C (b) 100°C [/question] [solution] Solution: (a) 250°C = gas (b) 100°C liquid as well as gas [/solution]...
Read More →$\mathrm{Fe}_{2} \mathrm{O}_{3}+2 \mathrm{Al} \rightarrow \mathrm{Al}_{2} \mathrm{O}_{3}+2 \mathrm{Fe}$
[question] Question. $\mathrm{Fe}_{2} \mathrm{O}_{3}+2 \mathrm{Al} \rightarrow \mathrm{Al}_{2} \mathrm{O}_{3}+2 \mathrm{Fe}$ The above reaction is an example of a (1) Combination reaction. (2) Double displacement reaction. (3) Decomposition reaction. (4) Displacement reaction. [/question] [solution] solution: (4) The given reaction is an example of a displacement reaction. [/solution]...
Read More →Convert the following temperature to Celsius scale :
[question] Question. Convert the following temperature to Celsius scale : (a) 300 K (b) 573 K [/question] [solution] Solution: (a) 300 – 273 = 27°C (b) 573 – 273 = 300°C [/solution]...
Read More →some title
Question: this is my question this is another line A $20 \mathrm{~cm}$ long capillary tube is dipped in water. The water rises up to $8 \mathrm{~cm}$. If the entire arrangement is put in a freely falling elevator the length of water column in the capillary tube will be option 1option 2 fsdfoption 4Correct Option: 4 Solution: this is solution...
Read More →Which of the statements about the reaction below are incorrect?
[question] Question. Which of the statements about the reaction below are incorrect? $2 \mathrm{PbO}(\mathrm{s})+\mathrm{C}(\mathrm{s}) \rightarrow 2 \mathrm{~Pb}(\mathrm{~s})+\mathrm{CO}_{2}(\mathrm{~g})$ (a) Lead is getting reduced. (b) Carbon dioxide is getting oxidised. (c) Carbon is getting oxidised. (d) Lead oxide is getting reduced. (1) (a) and (b) (2) (a) and (c) (3) (a), (b) and (c) (4) all [/question] [solution] solution: (1) (a) and (b) [/solution]...
Read More →Liquids generally have lower density as compared to solids.
[question] Question. Liquids generally have lower density as compared to solids. But you must have observed that ice floats on water. Find out why [/question] [solution] Solution: Ice is a solid but its density is lower than water due to its structure. The molecules in ice make a cage like structure with lot of vacant spaces, this makes ice float on water. [/solution]...
Read More →If the triangle ABC in the Question 7 above is revolved about the side 5 cm,
[question] Question. If the triangle ABC in the Question 7 above is revolved about the side 5 cm, then find the volume of the solid so obtained. Find also the ratio of the volumes of the two solids obtained in Questions 7 and 8. [/question] [solution] Solution: When right-angled $\triangle A B C$ is revolved about its side $5 \mathrm{~cm}$, a cone will be formed having radius $(r)$ as $12 \mathrm{~cm}$, height $(h)$ as $5 \mathrm{~cm}$, and slant height ( $l$ ) as $13 \mathrm{~cm}$. Volume of co...
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