Identify the solution among
[question] Question. Identify the solution among the following mixtures (a) Soil (b) Sea water (c) Air (d) Coal (e) Soda water [/question] [solution] Solution: Sea water, air, and soda water are solutions [/solution]...
Read More →What is a neutralisation reaction ?
[question] Question. What is a neutralisation reaction ? Give two examples. [/question] [solution] solution: A reaction in which an acid and base react with each other to give a salt and water is termed as neutralisation reaction. In this reaction, energy is evolved in the form of heat. For example, (ii) During indigestion (caused due to the production of excess of hydrochloric acid in the stomach),we administer an antacid (generally milk of magnesia, $\mathrm{Mg}(\mathrm{OH})_{2}$ which is basi...
Read More →Given below are the seats won by different political parties in the polling outcome of a state assembly elections:
[question] Question. Given below are the seats won by different political parties in the polling outcome of a state assembly elections: (i) Draw a bar graph to represent the polling results. (ii) Which political party won the maximum number of seats? [/question] [solution] Solution: (i) By taking polling results on x-axis and seats won as y-axis and choosing an appropriate scale (1 unit = 10 seats for y-axis), the required graph of the above information can be constructed as follows. Here, the r...
Read More →Which of the following materials fall in the category
[question] Question. Which of the following materials fall in the category of a "pure substance" ? (a) Ice (b) Milk (c) Iron (d) Hydrochloric acid (e) Calcium oxide (f) Mercury (g) Bric (h) Wood (i) Air. [/question] [solution] Solution: Ice, iron, hydrochloric acid, calcium oxide, and mercury are pure substances. [/solution]...
Read More →Show that any positive odd integer is of the form
[question] Question. Show that any positive odd integer is of the form $6 q+1$, or $6 q+3$ or $6 q+5$, where $q$ is some integer. [/question] [solution] Solution: Let us start with taking a, where a is any positive odd integer. We apply the divisionalgorithm, with a and b = 6. Since $0 \leq \mathrm{r}<6$, the possible remainders are 0, 1, 2, 3, 4, 5. That is, a can be 6q or 6q + 1, or 6q + 2, or 6q + 3, or 6q + 4, or 6q + 5, where q is the quotient. However, since a is odd, we do not consider th...
Read More →Plaster of Paris should be stored in a moisture-proof container.
[question] Question. Plaster of Paris should be stored in a moisture-proof container. Explain why? [/question] [solution] solution: Plaster of Paris should be stored in a moisture-proof container because Plaster of Paris, a powdery mass, absorbs water (moisture) to form a hard solid known as gypsum. [/solution]...
Read More →A milkman adds a very small amount of
[question] Question. A milkman adds a very small amount of baking soda to fresh milk. (a) Why does he shift the $\mathrm{pH}$ of the fresh milk from 6 to slightly alkaline? (b)Why does this milk take a long time to set as curd? [/question] [solution] solution: (a) The milkman shifts the $\mathrm{pH}$ of the fresh milk from 6 to slightly alkaline because in alkaline condition, milk does not set as curd easily. (b) Since this milk is slightly basic than usual milk, acids produced to set the curd a...
Read More →How would you confirm that a colourless liquid
[question] Question. How would you confirm that a colourless liquid given to you is pure water ? [question] [solution] Solution: If the boiling and freezing points of the given liquid comes out to be 100°C and 0°C respectively under one atmosphere pressure, it confirms that the given liquid is pure water [/solution]...
Read More →Fresh milk has a $\mathrm{pH}$ of 6 . How do you think the
[question] Question. Fresh milk has a $\mathrm{pH}$ of 6 . How do you think the $\mathrm{pH}$ will change as it turns into curd ? Explain your answer. [/question] [solution] solution: The $\mathrm{pH}$ of milk is $6 .$ As it changes to curd, the $\mathrm{pH}$ will reduce because curd is acidic in nature. The acids present in it decrease the $\mathrm{pH}$. [/solution]...
Read More →Classify each of the following as a homogeneous
[question] Question. Classify each of the following as a homogeneous or heterogeneous mixture. soda, water, wood, air, soil, vinegar, filtered tea. [/question] [solution] Solution: Homogeneous – soda, water, air, vinegar, filtered tea. Heterogeneous – wood, soil. [/solution]...
Read More →A company manufactures car batteries of a particular type
[question] Question. A company manufactures car batteries of a particular type. The lives (in years) of 40 such batteries were recorded as follows: 2.6 3.0 3.7 3.2 2.2 4.1 3.5 4.5 3.5 2.3 3.2 3.4 3.8 3.2 4.6 3.7 2.5 4.4 3.4 3.3 2.9 3.0 4.3 2.8 3.5 3.2 3.9 3.2 3.2 3.1 3.7 3.4 4.6 3.8 3.2 2.6 3.5 4.2 2.9 3.6 Construct a grouped frequency distribution table for this data, using class intervals of size 0.5 starting from the intervals 2 − 2.5. [/question] [solution] Solution: A grouped frequency tabl...
Read More →Explain the following by giving examples
[question] Question. Explain the following by giving examples (a) Saturated solution (b) Pure substance (c) Colloid (d) Suspension [/question] [solution] Solution: (a) At any particular temperature, a solution that has dissolved as much solute as it is capable of dissolving is said to be a saturated solution. Few examples of saturated solutions are soft drinks and nitrogen in Earth's soil. (b) A pure substance is one that cannot be separated into different constituents by physical or chemical pr...
Read More →Five solutions $\mathrm{A}, \mathrm{B}, \mathrm{C}, \mathrm{D}$ and $\mathrm{E}$ when tested
[question] Question. Five solutions A, B, C, D and E when tested with universal indicator showed pH as 4, 1, 11, 7 and 9 , respectively. Which solution is (a) neutral ? (b) strongly alkaline ? (c) strongly acidic ? (d) weakly acidic ? (e) weakly alkaline ? Arrange the pH in increasing order of hydrogen-ion concentration [/question] [solution] solution: (a) Neutral - Solution D with $\mathrm{pH} 7$ (b) Strongly alkaline - Solution C with pH 11 (c) Strongly acidic - Solution B with $\mathrm{pH} 1$...
Read More →Use Euclid's division algorithm to find the HCF of :
[question] Question. Use Euclid's division algorithm to find the HCF of : (i) 135 and 225 (ii) 196 and 38220 (iii) 867 and $225 .$ [/question] [solution] Solution: (i) 135 and $225 .$ Start with the larger integer, that is, 225. Apply the division lemma to 225 and 135, to get. $225=135 \times 1+90$ Since the remainder $90 \neq 0$, we apply the division lemma to 135 and 90 to get $135=90 \times 1+45$ We consider the new divisior 90 and the new remainder 45, and apply the division lemma to get $90...
Read More →Why do acids not show acidic behaviour
[question] Question. Why do acids not show acidic behaviour in the absence of water ? [/question] [solution] solution: Acids do not show acidic behaviour in the absence of water because there are no hydrogen ions available for conduction of electricity. Acids dissociate in the presence of water to give free hydrogen ions. It is the hydrogen ions that are responsible for the acidic behaviour. [/solution]...
Read More →The following data on the number of girls (to the nearest ten)
[question] Question. The following data on the number of girls (to the nearest ten) per thousand boys in different sections of Indian society is given below. (i) Represent the information above by a bar graph. (ii) In the classroom discuss what conclusions can be arrived at from the graph. [/question] [solution] Solution: (i) By representing section (variable) on x-axis and number of girls per thousand boys on y-axis, the graph of the information given above can be constructed by choosing an app...
Read More →Why does distilled water not conduct electricity,
[question] Question. Why does distilled water not conduct electricity, whereas rain water does? [/question] [solution] solution: Distilled water is a pure form of water and is devoid of any ionic species. Therefore, it does not conduct electricity. Rain water, being an impure form of water, contains many ionic species such as acids and therefore it conducts electricity. [/solution]...
Read More →Compounds such as alcohols and glucose also contain hydrogen but are not categorized as acids.
[question] Question. Compounds such as alcohols and glucose also contain hydrogen but are not categorized as acids. Describe an activity to prove it. [solution] solution: Acitivity Step 1- Two nails are fitted on a cork and are kept it in a 100 mL beaker. Step 2- The nails are then connected to the two terminals of a 6-volt battery through a bulb and a switch. Step 3- Some dilute HCl is poured in the beaker and the current is switched on. Step 4- The same experiment is then performed with glucos...
Read More →Pragya tested the solubility of three different substances at different
[question] Question. Pragya tested the solubility of three different substances at different temperatures and collected the data as given below. Result are given in the following table, as grams of substance dissolved in 100 grams of water to form a saturated solution. (a) Potassium nitrate would be needed to produce a saturated solution of potassium nitrate in 50 grams of water at 313 K ? (b) Pragya makes a saturated solution of potassium chloride in water at 353 K and leaves the solution to co...
Read More →A survey conducted by an organisation for the cause of illness and death among the women between the ages 15 − 44 (in years) worldwide,
[question] Question. A survey conducted by an organisation for the cause of illness and death among the women between the ages 15 − 44 (in years) worldwide, found the following figures (in %): (i) Represent the information given above graphically. (ii) Which condition is the major cause of women’s ill health and death worldwide? (iii) Try to find out, with the help of your teacher, any two factors which play a major role in the cause in (ii) above being the major cause. [/question] [solution] So...
Read More →Write word equations and then balanced equations
[question] Question. Write word equations and then balanced equations for the reaction taking place when - (1) Dilute sulphuric acid reacts with zinc granules. (2) Dilute hydrochloric acid reacts with magnesium ribbon. (3) Dilute sulphuric acid reacts with aluminium powder. (4) Dilute hydrochloric acid reacts with iron filings. [/question] [solution] solution: [/solution]...
Read More →A company manufactures car batteries of a particular type.
[question] Question. The following table gives the life times of neon lamps: 2.6 3.0 3.7 3.2 2.2 4.1 3.5 4.5 3.5 2.3 3.2 3.4 3.8 3.2 4.6 3.7 2.5 4.4 3.4 3.3 2.9 3.0 4.3 2.8 3.5 3.2 3.9 3.2 3.2 3.1 3.7 3.4 4.6 3.8 3.2 2.6 3.5 4.2 2.9 3.6 Construct a grouped frequency distribution table for this data, using class intervals of size 0.5 starting from the intervals 2 − 2.5. [/question] [solution] Solution: A grouped frequency table of class size 0.5 has to be constructed, starting from class interval...
Read More →Which one of the following types of medicines
[question] Question. Which one of the following types of medicines is used for treating indigestion ? (1) Antibiotic (2) Analgesic (3) Antacid (4) Antiseptic [/question] [solution] solution: (3) Antacid [/solution]...
Read More →Write the steps you would use for making tea.
[question] Question. Write the steps you would use for making tea. Use the words solution, solvent, solute, dissolve, soluble, insoluble, filtrate and residue. [/question] [solution] Solution: Take some water in pan. Keep the pan over flame. The solutes tea leaves & sugar should be added to a pan containing water as solvent. Heat the water over the pan till the sugar, which is soluble in water dissolves in it. Tea leaves are insoluble in water and will remain suspended. Now add water to the suga...
Read More →A solution reacts with crushed egg-shells to give a gas that turns lime-water milky.
[question] Question. A solution reacts with crushed egg-shells to give a gas that turns lime-water milky. The solution contains (1) NaCl (2) HCl (3) LiCl (4) KCl [/question] [solution] solution: (2) HCl [/solution]...
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