Which separation techniques will you apply for the separation
[question] Question. Which separation techniques will you apply for the separation of the following ? (a) Sodium chloride from its solution in water. (b) Ammonium chloride from a mixture containing sodium chloride and ammonium chloride. (c) Small piece of metal in the engine oil of a car. (d) Different pigments from an extract of flower petals. (e) Butter from curd. (f) Oil from curd. (g) Tea leaves from tea (h) Iron pins from sand. (i) Wheat grains from husk. (j) Fine mud particles suspended in...
Read More →A solution turns red litmus blue,
[question] Question. A solution turns red litmus blue, its $\mathrm{pH}$ is likely to be (1) 1 (2) 4 (3) 5 (4) 10 [/question] [solution] solution: (4) 10...
Read More →Write an equation to show the reaction between
[question] Question. Write an equation to show the reaction between Plaster of Paris and water. [/question] [solution] solution: The chemical equation for the reaction of Plaster of Paris and water can be represented as [/solution]...
Read More →Thirty children were asked about the number of hours they watched TV programmes in the previous week.
[question] Question. Thirty children were asked about the number of hours they watched TV programmes in the previous week. The results were found as follows: 1 6 2 3 5 12 5 8 4 8 10 3 4 12 2 8 15 1 17 6 3 2 8 5 9 6 8 7 14 12 (i) Make a grouped frequency distribution table for this data, taking class width 5 and one of the class intervals as 5 - 10. (ii) How many children watched television for 15 or more hours a week? [solution] Solution: (i) Our class intervals will be 0 − 5, 5 − 10, 10 −15….. ...
Read More →What will happen if a solution of sodium hydrogen carbonate is heated?
[question] Question. What will happen if a solution of sodium hydrogen carbonate is heated? Give the equation of the reaction involved. [/question] [solution] solution: When a solution of sodium hydrogencarbonate is heated, sodium carbonate and water are formed with the evolution of carbon dioxide gas. <img src="/media/uploads/2021/12/What-will-happen-if-a-solution-of-sodium-hydrogen-carbonate.png" alt="What will happen if a solution of sodium hydrogen carbonate " [/solution]...
Read More →Name the sodium compound
[question] Question. Name the sodium compound which is used for softening hard water. [/question] [solution] solution: Washing soda $\left(\mathrm{Na}_{2} \mathrm{CO}_{3} \cdot 10 \mathrm{H}_{2} \mathrm{O}\right)$ is used for softening hard water. [/solution]...
Read More →Name the substance which on treatment
[question] Question. Name the substance which on treatment with chlorine yields bleaching powder ? [/question] [solution] solution: Calcium hydroxide $\left[\mathrm{Ca}(\mathrm{OH})_{2}\right]$, on treatment with chlorine, yields bleaching powder. [/solution]...
Read More →What is the common name of the compound
[question] Question. What is the common name of the compound $\mathrm{CaOCl}_{2}$ ? [/question] [solution] solution: The common name of the compound $\mathrm{CaOCl}_{2}$ is bleaching powder. [/solution]...
Read More →The value of π up to50 decimal places is given below:
[question] Question. The value of π up to50 decimal places is given below: 3.14159265358979323846264338327950288419716939937510 (i) Make a frequency distribution of the digits from 0 to 9 after the decimal point. (ii) What are the most and the least frequently occurring digits? The value of π up to50 decimal places is given below: [solution] Solution: (i) By observation of the digits after decimal point, the required table can be constructed as follows. (ii) It can be observed from the above tab...
Read More →Under what soil condition do you think a farmer would
[question] Question. Under what soil condition do you think a farmer would treat the soil of his fields with quick lime (calcium oxide) or slaked lime (calcium hydroxide) or chalk (calcium carbonate) ? [/question] [solution] solution: If the soil is acidic and improper for cultivation, then to neutralise the acidity of the soil, the farmer would treat the soil with quick lime or slaked lime or chalk. [/solution]...
Read More →Do basic solutions also have $\mathrm{H}^{+}(\mathrm{aq})$ ions ?
[question] Question. Do basic solutions also have $\mathrm{H}^{+}(\mathrm{aq})$ ions ? If yes, then why are these basic ? [/question] [solution] solution: Yes, a basic solution also has $\mathrm{H}^{+}(\mathrm{aq})$ ions. However, their concentration is less as compared to the concentration of $\mathrm{OH}^{-}(\mathrm{aq})$ ions which makes the solution basic. [/solution]...
Read More →Three coins were tossed 30 times simultaneously.
[question] Question. Three coins were tossed 30 times simultaneously. Each time the number of heads occurring was noted down as follows: 0 1 2 2 1 2 3 1 3 0 1 3 1 1 2 2 0 1 2 1 3 0 0 1 1 2 3 2 2 0 Prepare a frequency distribution table for the data given above. [solution] Solution: By observing the data given above, the required frequency distribution table can be constructed as follows. [/solution]...
Read More →What effect does the concentration
[question] Question. What effect does the concentration of $\mathrm{H}^{+}$(aq) ions have on the nature of the solution ? [/question] [solution] solution: If the concentration of $\mathrm{H}^{+}$ions is increased, the solution becomes more acidic. If the concentration of $\mathrm{H}^{+}$ions is decreased, the solution becomes less acidic or more basic. [/solution]...
Read More →A study was conducted to find out the concentration of sulphur dioxide in the air in parts per million (ppm) of a certain city.
[question] Question. A study was conducted to find out the concentration of sulphur dioxide in the air in parts per million (ppm) of a certain city. The data obtained for 30 days is as follows: 0.03 0.08 0.08 0.09 0.04 0.17 0.16 0.05 0.02 0.06 0.18 0.20 0.11 0.08 0.12 0.13 0.22 0.07 0.08 0.01 0.10 0.06 0.09 0.18 0.11 0.07 0.05 0.07 0.01 0.04 (i) Make a grouped frequency distribution table for this data with class intervals as 0.00 - 0.04, 0.04 - 0.08, and so on. (ii) For how many days, was the c...
Read More →The heights of 50 students,
[question] Question. The heights of 50 students, measured to the nearest centimeters, have been found to be as follows: 161 150 154 165 168 161 154 162 150 151 162 164 171 165 158 154 156 172 160 170 153 159 161 170 162 165 166 168 165 164 154 152 153 156 158 162 160 161 173 166 161 159 162 167 168 159 158 153 154 159 (i) Represent the data given above by a grouped frequency distribution table, taking the class intervals as 160 - 165, 165 - 170, etc. (ii) What can you conclude bout their heights...
Read More →The relative humidity (in %) of a certain city for a month of 30 days was as follows:
[question] Question. The relative humidity (in %) of a certain city for a month of 30 days was as follows: 98.1 98.6 99.2 90.3 86.5 95.3 92.9 96.3 94.2 95.1 89.2 92.3 97.1 93.5 92.7 95.1 97.2 93.3 95.2 97.3 96.2 92.1 84.9 90.2 95.7 98.3 97.3 96.1 92.1 89 (i) Construct a grouped frequency distribution table with classes 84 - 86, 86 - 88 (ii) Which month or season do you think this data is about? (iii) What is the range of this data? [solution] Solution: (i) A grouped frequency distribution table ...
Read More →How is the concentration of hydroxide ions
[question] Question. How is the concentration of hydroxide ions $\left(\mathrm{OH}^{-}\right)$affected when excess base is dissolved in a solution of sodium hydroxide ? [/question] [solution] solution: The concentration of hydroxide ions $\left(\mathrm{OH}^{-}\right)$would increase when excess base is dissolved in a solution of sodium hydroxide. [/solution]...
Read More →The distance (in km) of 40 engineers from their residence to their place of work were found as follows:
[question] Question. The distance (in km) of 40 engineers from their residence to their place of work were found as follows: 5 3 10 20 25 11 13 7 12 31 19 10 12 17 18 11 32 17 16 2 7 9 7 8 3 5 12 15 18 3 12 14 2 9 6 15 15 7 6 12 Construct a grouped frequency distribution table with class size 5 for the data given above taking the first interval as 0 - 5 (5 not included). What main feature do you observe from this tabular representation? [solution] Solution: It is given that a grouped frequency d...
Read More →How is the concentration of hydronium ions
[question] Question. How is the concentration of hydronium ions $\left(\mathrm{H}_{3} \mathrm{O}^{+}\right)$affected when a solution of an acid is diluted [/question] [solution] solution: When an acid is diluted, the concentration of hydronium ions $\left(\mathrm{H}_{3} \mathrm{O}^{+}\right)$per unit volume decreases. This means that the strength of the acid decreases. [/solution]...
Read More →The blood groups of 30 students of Class VIII are recoded as follows:
[question] Question. The blood groups of 30 students of Class VIII are recoded as follows: A, B, O, O, AB, O, A, O, B, A, O, B, A, O, O, A, AB, O, A, A, O, O, AB, B, A, O, B, A, B, O. Represent this data in the form of a frequency distribution table. Which is the most common, and which is the rarest, blood group among these students? [solution] Solution: It can be observed that 9 students have their blood group as A, 6 as B, 3 as AB, and 12 as O. Therefore, the blood group of 30 students of the ...
Read More →While diluting an acid,
[question] Question. While diluting an acid, why is it recommended that the acid should be added to water and not water to the acid ? [/question] [solution] solution: It is recommended that the acid should be added to water and not water to the acid because the process of dissolving an acid in water is exothermic.If water is added to acid, since large amount of acid is present, a large amount of heat is generated, therefore, themixture splashes out and causes burns. [/solution]...
Read More →Classify the data in Q1 above as primary or secondary data.
[question] Question. Classify the data in Q1 above as primary or secondary data. [/question] [solution] Solution: The information which is collected by the investigator himself with a definite objective in his mind is called as primary data whereas when the information is gathered from a source which already had the information stored, it is called as secondary data. It can be observed that the data in 1, 3, and 5 is secondary data and the data in 2 and 4 is primary data. [/solution]...
Read More →While diluting an acid,
[question] Question. While diluting an acid, why is it recommended that the acid should be added to water and not water to the acid ? [/question] [solution] solution: It is recommended that the acid should be added to water and not water to the acid because the process of dissolving an acid in water is exothermic.If water is added to acid, since large amount of acid is present, a large amount of heat is generated, therefore, themixture splashes out and causes burns. [/solution]...
Read More →Give five examples of data that you can collect from day to day life.
[question] Question. Give five examples of data that you can collect from day to day life. [/question] [solution] Solution: In our day to day life, we can collect the following data. 1. Number of females per 1000 males in various states of our country 2. Weights of students of our class 3. Production of wheat in the last 10 years in our country 4. Number of plants in our locality 5. Rainfall in our city in the last 10 years [/solution]...
Read More →Why does dry HCl gas not change
[question] Question. Why does dry HCl gas not change the colour of the dry litmus paper ? [/question] [solution] solution: Acid do not ionize in the absence of water to liberate $\mathrm{H}_{3} \mathrm{O}^{+}$which shows acidic nature of a solution. Therefore, dry $\mathrm{HCl}$ gas does not change the colour of the dry litmus paper because it does not contain $\mathrm{H}^{+}$ions. [/solution]...
Read More →