eSaral - JEE | NEET | Class 8-10 Exam Prep App

Define a taxon.

[question] Question. Define a taxon. Give some examples of taxa at different hierarchical levels. [/question] [solution] Solution: Each unit or category of classification is termed as a taxon. It represents a rank. For example, the basic level of classification is species, followed by genus, family, order, class, phylum or division, in ascending order. The highest level of classification is known as kingdom. [/solution]...

How much copper can be obtained from 100 g of copper sulphate (CuSO4)?

[question] Question. How much copper can be obtained from 100 g of copper sulphate (CuSO4)? [/question] [solution] Solution: 1 mole of $\mathrm{CuSO}_{4}$ contains 1 mole of copper. Molar mass of CuSO4= (63.5) + (32.00) + 4(16.00) = 63.5 + 32.00 + 64.00 = 159.5 g 159.5 g of CuSO4contains 63.5 g of copper $\Rightarrow 100 \mathrm{~g}$ of $\mathrm{CuSO}_{4}$ will contain $\frac{63.5 \times 100 \mathrm{~g}}{159.5}$ of copper. $\therefore$ Amount of copper that can be obtained from $100 \mathrm{~g} ...

Find the values of k for each of the following quadratic equations,

[question] Question. Find the values of k for each of the following quadratic equations, so that they have two real equal roots. (i) $2 x^{2}+k x+3=0$ (ii) $k x(x-2)+6=0$ [/question] [solution] Solution: (i) $2 x^{2}+k x+3=0$ $\mathrm{a}=2, \mathrm{~b}=\mathrm{k}, \mathrm{c}=3$ $\mathrm{D}=\mathrm{b}^{2}-4 \mathrm{ac}=\mathrm{k}^{2}-4 \times 2 \times 3=\mathrm{k}^{2}-24$ Two roots will be equal if $D=0$, i.e., if $k^{2}-24=0$ i.e., if $k^{2}-24$, i.e., if $k=\pm \sqrt{\mathbf{2 4}}$ i.e., if $\m...

Given below is the scientific name of Mango.

[question] Question. Given below is the scientific name of Mango. Identify the correctly written name. Mangifera Indica Mangifera indica [/question] [solution] Solution: In binomial system of nomenclature, the generic name of a species always starts with a capital letter whereas the specific name starts with a small letter. Therefore, the correct scientific name of Mango is Mangifera indica. [/solution]...

Calculate the concentration of nitric acid in moles

[question] Question. Calculate the concentration of nitric acid in moles per litre in a sample which has a density, $1.41 \mathrm{~g} \mathrm{~mL}^{-1}$ and the mass per cent of nitric acid in it being $69 \%$. [/question] [solution] Solution: Mass percent of nitric acid in the sample = 69 % [Given] Thus, 100 g of nitric acid contains 69 g of nitric acid by mass. Molar mass of nitric acid (HNO3) $=\{1+14+3(16)\} \mathrm{g} \mathrm{mol}^{-1}$ = 1 + 14 + 48 $=63 \mathrm{~g} \mathrm{~mol}^{-1}$ Num...

Find the nature of the roots of the following quadratic equations.

[question] Question. Find the nature of the roots of the following quadratic equations. If the real roots exist, find them : (i) $2 x^{2}-3 x+5=0$ (ii) $3 x^{2}-4 \sqrt{3} x+4=0$ (iii) $2 x^{2}-6 x+3=0$ [/question] [solution] Solution: (i) $2 x^{2}-3 x+5=0$ $\mathrm{a}=2, \mathrm{~b}=-3, \mathrm{c}=5$ Discriminant $\mathrm{D}=\mathrm{b}^{2}-4 \mathrm{ac}=9-4 \times 2 \times 5$ $=9-40=-31$ $\Rightarrow \mathrm{D}<0$ Hence, no real root. (ii) $3 x^{2}-4 \sqrt{3} x+4=0$ $a=3, b=-4 \sqrt{3}, c=4$ Di...

What do we learn from identification of individuals and populations?

[question] Question. What do we learn from identification of individuals and populations? [/question] [solution] Solution: The knowledge of characteristics of an individual or its entire population helps in the identification of similarities and dissimilarities among the individuals of same kind or between different types of organisms. It helps the scientists to classify organisms in various categories. [/solution]...

What different criteria would you choose to classify people that you meet often?

[question] Question. What different criteria would you choose to classify people that you meet often? [/question] [solution] Solution: To classify a class of forty students, let us start the classification on the basis of sexes of the students. This classification will result in the formation of two major groups- boys and girls. Each of these two groups can be further classified on the basis of the names of the students falling in these groups. Since it is possible that more than one student can...

Why are the classification systems changing every now and then?

[question] Question. Why are the classification systems changing every now and then? [/question] [solution] Solution: Millions of plants, animals, and microorganisms are found on earth. Many of these have been identified by the scientists while many new species are still being discovered around the world. Therefore, to classify these newly discovered species, new systems of classification have to be devised every now and then. This creates the requirement to change the existing systems of classi...

Sum of the area of two squares is $468 \mathrm{~m}^{2}$.

[question] Question. Sum of the area of two squares is $468 \mathrm{~m}^{2}$. If the difference of their perimeters is $24 \mathrm{~m}$, find the sides of the two squares. [/question] [solution] Solution: Let the sides of the two squares be $x \mathrm{~m}$ and $y \mathrm{~m}$. Therefore, their perimeter will be $4 x$ and $4 y$ respectively and their areas will be $x^{2}$ and $y^{2}$ respectively. It is given that $4 x-4 y=24$ $x-y=6$ $x=y+6$ Also, $x^{2}+y^{2}=468$ $\Rightarrow(6+y)^{2}+y^{2}=46...

Why are living organisms classified?

[question] Question. Why are living organisms classified? [question] [solution] Solution: A large variety of plants, animals, and microbes are found on earth. All these living organisms differ in size, shape, colour, habitat, and many other characteristics. As there are millions of living organisms on earth, studying each of them is impossible. Therefore, scientists have devised mechanisms to classify all living organisms. These methods of classification are based on rules and principles that al...

Calculate the mass of sodium acetate $\left(\mathrm{CH}_{3} \mathrm{COONa}\right)$ required to make

[question] Question. Calculate the mass of sodium acetate $\left(\mathrm{CH}_{3} \mathrm{COONa}\right)$ required to make $500 \mathrm{~mL}$ of $0.375$ molar aqueous solution. Molar mass of sodium acetate is $82.0245 \mathrm{~g} \mathrm{~mol}^{-1}$ [/question] [solution] Solution: 0.375 M aqueous solution of sodium acetate ≡ 1000 mL of solution containing 0.375 moles of sodium acetate Number of moles of sodium acetate in 500 mL Molar mass of sodium acetate $=82.0245 \mathrm{~g}$ mole $^{-1}$ (Giv...

How do you differentiate betwee n capture fishing, mariculture, and aquaculture.

[question] Question. How do you differentiate betwee n capture fishing, mariculture, and aquaculture. [/question] [solution] Solution: Capture fishery is the process of obtaining fish from natural resources i.e. river, pond, etc. Mariculture is the culture of marine fish while, aquaculture is cultivation of aquatic organisms in fresh water. [/solution]...

For increasing production, what is common in poultry, fisheries and bee-keeping ?

[question] Question. For increasing production, what is common in poultry, fisheries and bee-keeping ? [/question] [solution] Solution: Most common method of increasing production is developing improved varieties through cross breeding, which is a method of producing an organism with all the desired traits including high production, disease resistance, etc. Management practices include : breeding, feeding, shelter and heeding. [/solution]...

Calculate the amount of carbon dioxide that could be produced when

[question] Question. Calculate the amount of carbon dioxide that could be produced when (i)1 mole of carbon is burnt in air. (ii)1 mole of carbon is burnt in 16 g of dioxygen. (iii)2 moles of carbon are burnt in 16 g of dioxygen [/question] [solution] Solution: The balanced reaction of combustion of carbon can be written as: (i) As per the balanced equation, 1 mole of carbon burns in1 mole of dioxygen (air) to produce1 mole of carbon dioxide. (ii) According to the question, only 16 g of dioxygen...

A train travels 360 km at a uniform speed.

[question] Question. A train travels 360 km at a uniform speed. If the speed had been 5 km/hr more, it would have taken I hour less for the same journey. Find the speed of the train. [/question] [solution] Solution: Let the speed of the train be x km/hr. We are given that 360 km distance is to be travelled at uniform speed of x km/hr. Time taken to cover the distance of $360 \mathrm{~km}=\frac{\mathbf{3 6 0}}{\mathbf{x}}$ hours. In case, the speed is increased by $5 \mathrm{~km} / \mathrm{hr}$, ...

What are the benefits of cattle farming ?

[question] Question. What are the benefits of cattle farming ? [/question] [solution] Solution: Through cattle farming we can get :- 1. High milk-yeilding animals. 2. Animals which produce good quality of meat, fibre and skin 3. Good breed of draught animals [/solution]...

The position-time $(x-t)$ graphs for two children $A$ and $B$

[question] Question. The position-time $(x-t)$ graphs for two children $A$ and $B$ returning from their school $O$ to their homes $P$ and $Q$ respectively are shown in Fig. 3.19. Choose the correct entries in the brackets below; (a) (A/B) lives closer to the school than (B/A) (b) (A/B) starts from the school earlier than (B/A) (c) (A/B) walks faster than (B/A) (d) A and B reach home at the (same/different) time (e) (A/B) overtakes (B/A) on the road (once/twice). [/question] [solution] solution: ...

How do good animal husbandry practices benefit farmers ?

[question] Question. How do good animal husbandry practices benefit farmers ? [/question] [solution] Solution: Good animal husbandry practices benefit farmers by providing:- 1. High milk-yeilding breeds of cows and buffaloes. 2. Dual purpose breeds i.e., cows for milk and bullocks for draught work. 3. Disease resistant varieties of animals. [/solution]...

The difference of squares of two numbers is 180.

[question] Question. The difference of squares of two numbers is 180. The square of the smaller number is 8 times the larger number. Find the two numbers [/question] [solution] Solution: Let the larger and smaller number be x and y respectively. According to the given question, $x^{2}-y^{2}=180$ and $y^{2}=8 x$ $\Rightarrow x^{2}-8 x=180$ $\Rightarrow x^{2}-8 x-180=0$ $\Rightarrow x^{2}-18 x+10 x-180=0$ $\Rightarrow x(x-18)+10(x-18)=0$ $\Rightarrow(x-18)(x+10)=0$ $\Rightarrow x=18,-10$ However, ...

How do storage grain losses occur ?

[question] Question. How do storage grain losses occur ? [/question] [solution] Solution: Factors which are responsible for losses of grains during storage are both biotic and abiotic. Biotic factors responsible for such losses are - insects, rodents, fungi, mites and bacteria and abiotic factors are inappropriate moisture and temperature in place of storage. [/solution]...

Determine the empirical formula of an oxide of iron which has 69.9%

[question] Question. Determine the empirical formula of an oxide of iron which has 69.9% iron and 30.1% dioxygen by mass [/question] [solution] Solution: % of iron by mass = 69.9 % [Given] % of oxygen by mass = 30.1 % [Given] Relative moles of iron in iron oxide Relative moles of oxygen in iron oxide Simplest molar ratio of iron to oxygen = 1.25: 1.88 = 1: 1.5 = 2: 3 $\therefore$ The empirical formula of the iron oxide is $\mathrm{Fe}_{2} \mathrm{O}_{3}$. [/solution]...

The diagonal of a rectangular field is 60 metres more than the shorter side.

[question] Question. The diagonal of a rectangular field is 60 metres more than the shorter side. If the longer side is 30 metres more than the shorter side, find the sides of the field. [/question] [solution] Solution: In rectangle ABCD, let the shorter side BC = x metres. Then AB = (x + 30) metres and diagonal AC = (x + 60) metres. By Pythagoras Theorem we have $\mathrm{AB}^{2}+\mathrm{BC}^{2}=\mathrm{AC}^{2}$ $\Rightarrow(x+30)^{2}+x^{2}$ $=(x+60)^{2}$ $\Rightarrow x^{2}+60 x+900+x^{2}$ $=x^{...

What is genetic manipulation ? How is it useful in argicultural practices ?

[question] Question. What is genetic manipulation ? How is it useful in argicultural practices ? [/question] [solution] Solution: A process in which genes of desirable characters are taken from a plant and transferred to another plant which lacks these genes, leading to the production of varieties with desirable agronomic characteristics like dwarfness in cereals, and tallness and profuse branching in case of fodder crops. Genetic mainpulation is useful in developing varieties with:- (i) Higher ...

What are the advantages of inter-cropping and crop rotation ?

[question] Question. What are the advantages of inter-cropping and crop rotation ? [question] [solution] Solution: Using Inter-cropping as a method of crop production ensures the following advantages :- 1. Productivity is increased 2. It economises space and time of cultivating two or more crops. 3. It helps to maintain soil fertility. While crop rotation confers following benefits : 1. By growing crops in rotation, the fertility of the soil is utilised more evenly. The soil is not depleted in a...

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