The following data are obtained when dinitrogen and dioxygen react together to form different compounds
[question] Question. The following data are obtained when dinitrogen and dioxygen react together to form different compounds (a)Which law of chemical combination is obeyed by the above experimental data?Give its statement (b)Fill in the blanks in the following conversions (i) $\quad 1 \mathrm{~km}=\ldots \ldots \ldots \ldots \ldots \ldots . \mathrm{mm}=\ldots \ldots \ldots \ldots \ldots \ldots . \mathrm{pm}$ (ii) $1 \mathrm{mg}=\ldots \ldots \ldots \ldots \ldots \ldots \ldots \mathrm{kg}=\ldots ...
Read More →An AP consists of 50 terms of which 3rd term is 12 and the last term is 106.
[question] Question. An AP consists of 50 terms of which $3 \mathrm{rd}$ term is 12 and the last term is 106 . Find the 29 th term. [/question] [solution] Solution: $\mathrm{t}_{3}=12, \mathrm{t}_{50}$ (last term) $=106$ $\Rightarrow a+2 d=12$ ..(1) and $a+49 d=106$ ...(2) Subtracting (1) from (2), we get $47 \mathrm{~d}=106-12=94 \Rightarrow \mathrm{d}=2$ From (1), a + 2 × 2 =12 $\quad \Rightarrow a=8$ $\mathrm{t}_{29}=\mathrm{a}+28 \mathrm{~d}=8+28 \times 2=64$ [/solution]...
Read More →Find the 31st term of an AP whose 11th term is 38 and the 16th term is 73.
[question] Question. Find the 31st term of an AP whose 11th term is 38 and the 16th term is 73. [/question] [solution] Solution: Given that, $a_{11}=38$ $a_{16}=73$ We know that, $a_{n}=a+(n-1) d$ $a_{11}=a+(11-1) d$ $38=a+10 d$ ..(1) Similarly, $a_{16}=a+(16-1) d$ $73=a+15 d$ $73=a+15 d$ ...(2) On subtracting (1) from (2), we obtain $35=5 \mathrm{~d}$ $d=7$ From equation (1), $38=a+10 \times(7)$ $38-70=a$ $a=-32$ $a_{31}=a+(31-1) d$ $=-32+30(7)$ $=-32+210$ $=178$ Hence, $31^{\text {st }}$ term ...
Read More →Give a comparative account of the classes of Kingdom Fungi under the following:
[question] Question. Give a comparative account of the classes of Kingdom Fungi under the following: (i) Mode of nutrition (ii) Mode of reproduction [solution] Solution: (A) Phycomycetes- This group of fungi includes members such as Rhizopus, Albugo, etc. (i) Mode of nutrition They are obligate parasites on plants or are found on decaying matter such as wood. (ii) Mode of reproduction Asexual reproduction takes place through motile zoospores or non-motile aplanospores that are produced endogenou...
Read More →Check whether – 150 is a term of the AP
[question] Question. Check whether – 150 is a term of the AP : 11, 8, 5, 2, .... . [/question] [solution] Solution: $a=11, d=-3$ Let if possible $\mathrm{t}_{\mathrm{n}}=-150$ $\Rightarrow a+(n-1) d=-150$ $\Rightarrow 11+(n-1) \times(-3)=-150$ $\Rightarrow 11-3 n+3=-150$ $\Rightarrow 14-3 n=-150$ $\Rightarrow 3 n=14+150=164$ $\Rightarrow \mathrm{n}=\frac{164}{3}=54 \frac{2}{3}$ It is not possible because n is to be natural number. Hence, – 150 cannot be a term of the AP. [/solution]...
Read More →What do the terms phycobiont and mycobiont signify?
[question] Question. What do the terms phycobiont and mycobiont signify? [/question] [solution] Solution: Phycobiont refers to the algal component of the lichens and mycobiont refers to the fungal component. Algae contain chlorophyll and prepare food for fungi whereas the fungus provides shelter to algae and absorbs water and nutrients from the soil. This type of relationship is referred to as symbiotic. [/solution]...
Read More →Find the number of terms in each of the following AP's :
[question] Question. Find the number of terms in each of the following AP's : (i) $7,13,19 \ldots \ldots, 205$ (ii) $18,15 \frac{1}{2}, 13, \ldots,-47$ [/question] [solution] Solution: (i) $\mathrm{a}=7, \mathrm{~d}=6$, $t_{n}=205$ $\Rightarrow a+(n-1) d=205$ $\Rightarrow 7+(n-1) \times 6=205 \quad \Rightarrow 6 n+1=205$ $\Rightarrow 6 n=204 \quad \Rightarrow n=34$ Hence, 34 terms (ii) $a=18$ $\mathrm{d}=\mathrm{a}_{2}-\mathrm{a}_{1}=15 \frac{1}{2}-18$ $\mathrm{d}=\frac{31-36}{2}=-\frac{5}{2}$ L...
Read More →Plants are autotrophic. Can you think of some plants that are partially heterotrophic?
[question] Question. Plants are autotrophic. Can you think of some plants that are partially heterotrophic? [/question] [solution] Solution: Plants have autotrophic mode of nutrition as they contain chlorophyll pigment. Thus, they have the ability to prepare their own food by the process of photosynthesis. However, some insectivorous plants are partially heterotrophic. They have various means of capturing insects so as to supplement their diet with required nutrients derived from insects, causin...
Read More →Round up the following upto three significant figures
[question] Question. Round up the following upto three significant figures (i)34.216 (ii)10.4107 (iii)0.04597 (iv)2808 [/question] [solution] Solution: (i)34.2 (ii)10.4 (iii)0.0460 (iv)2810 [/solution]...
Read More →Describe briefly the four major groups of Protozoa.
[question] Question. Describe briefly the four major groups of Protozoa. [/question] [solution] Solution: Protozoa are microscopic unicellular protists with heterotrophic mode of nutrition. They may be holozoic, saprobic, or parasitic. These are divided into four major groups. (1) Amoeboid protozoa or sarcodines They are unicellular, jelly-like protozoa found in fresh or sea water and in moist soil. Their body lacks a periplast. Therefore, they may be naked or covered by a calcareous shell. They...
Read More →Which term of the AP :
[question] Question. Which term of the AP : 3, 8, 13, 18, ... is 78? [/question] [solution] Solution: $a=3, d=5$ Let $\mathrm{t}_{\mathrm{n}}=78$ $\Rightarrow a+(n-1) d=78$ $\Rightarrow 3+(n-1) \times 5=78 \Rightarrow 5 n-2=78$ $\Rightarrow 5 \mathrm{n}=80 \quad \Rightarrow \mathrm{n}=16$ Hence, $\mathrm{t}_{16}=78$ [/solution]...
Read More →How are viroids different from viruses?
[question] Question. How are viroids different from viruses? [/question] [solution] Solution: Viroids were discovered in 1917 by T.O. Denier. They cause potato spindle tuber disease. They are smaller in size than viruses. They also lack the protein coat and contain free RNA of low molecular weight. [/solution]...
Read More →In the following APs,
[question] Question. In the following APs, find the missing terms in the boxes : (i) $2, \square, 26$ (ii) $\square, 13, \square, 3$ (iii) $5, \square, \square, 9 \frac{1}{2}$ (iv) $-4, \square, \square, \square, \square, 6$ (v) $\square, 38, \square, \square, \square,-22$ [/question] [solution] Solution: (i) $\mathrm{a}=2, \mathrm{a}+2 \mathrm{~d}=26 \quad \Rightarrow 2+2 \mathrm{~d}=26$ $\Rightarrow 2 \mathrm{~d}=26-2=24 \quad \Rightarrow \mathrm{d}=12$ Then the missing term $t_{2}=a+d=2+12=14...
Read More →How many significant figures are present in the following
[question] Question. How many significant figures are present in the following (i) $0.0025$ (ii) 208 (iii) 5005 (iv) 126,000 (v) $500.0$ (vi) $2.0034$ [/question] [solution] Solution: (i)0.0025 There are 2 significant figures. (ii)208 There are 3 significant figures. (iii)5005 There are 4 significant figures. (iv)126,000 There are 3 significant figures. (v)500.0 There are 4 significant figures. (vi)2.0034 There are 5 significant figure [/solution]...
Read More →Suggest a suitable physical situation for each of the following graphs
[question] Question. Suggest a suitable physical situation for each of the following graphs [/question] [solution] solution: (a) The given $x-t$ graph shows that initially a body was at rest. Then, its velocity increases with time and attains an instantaneous constant value. The velocity then reduces to zero with an increase in time. Then, its velocity increases with time in the opposite direction and acquires a constant value. A similar physical situation arises when a football (initially kept ...
Read More →Express the following in the scientific notation
[question] Question. Express the following in the scientific notation (i) $0.0048$ (ii) 234,000 (iii) 8008 (iv) $500.0$ (v) $6.0012$ [/question] [solution] Solution: (i) $0.0048=4.8 \times 10^{-3}$ (ii) $234,000=2.34 \times 10^{5}$ (iii) $8008=8.008 \times 10^{3}$ (iv) $500.0=5.000 \times 10^{2}$ (v) $6.0012=6.0012$ [/solution]...
Read More →A sample of drinking water was foundto be severely contaminated with chloroform,
[question] Question. A sample of drinking water was found to be severely contaminated with chloroform, $\mathrm{CHCl}_{3}$, supposed to be carcinogenic in nature. The level of contamination was 15 ppm (by mass) (i)Express this in percent by mass. (ii)Determine the molality of chloroform in the water sample. [/question] [solution] Solution: (i) $1 \mathrm{ppm}$ is equivalent to 1 part out of 1 million $\left(10^{6}\right)$ parts. Mass percent of 15 ppm chloroform in water $=\frac{15}{10^{6}} \tim...
Read More →Choose the correct choice in the following and justify
[question] Question. Choose the correct choice in the following and justify (i) 30th term of the AP: $10,7,4, \ldots$ is (A) 97 (B) 77 (C) $-77$ (D) $-87$ (ii) 11th term of the AP: $-3,-\frac{1}{2}, 2, \ldots$ is (A) 28 (B) 22 (C) $-38$ (D) $-48 \frac{1}{2}$ [/question] [solution] Solution: (i) $a=10, d=-3$ $\mathrm{t}_{30}=\mathrm{a}+29 \mathrm{~d}=10+29 \times(-3)$ $=10-87=-77$ Hence, the correct option is (C) (ii) $\mathrm{a}=-3, \mathrm{~d}=5 / 2$ $\mathrm{t}_{11}=\mathrm{a}+10 \mathrm{~d}=-...
Read More →Figure $3.21$ shows the $x-t$ plot of one-dimensional motion of a particle.
[question] Question. Figure $3.21$ shows the $x-t$ plot of one-dimensional motion of a particle. Is it correct to say from the graph that the particle moves in a straight line for $t0$ ? If not, suggest a suitable physical context for this graph. [/question] [solution] solution: The $x-t$ graph of a particle moving in a straight line for $t0$ cannot be shown as the given graph. This is because, the given particle does not follow the trajectory of path followed by the particle as $t=0, x=0$. A ph...
Read More →Fill in the blanks in the following table,
[question] Question. Fill in the blanks in the following table, given that a is the first term, $d$ the common difference and $a_{n}$, the $n^{\text {th }}$ term of the AP. [/question] [solution] Solution: (i) $\mathrm{a}=7, \mathrm{~d}=3, \mathrm{n}=8$ $a_{8}=a+7 d=7+7 \times 3=28$ Hence, $a_{8}=28$. (ii) $\mathrm{a}=-18, \mathrm{n}=10, \mathrm{a}_{\mathrm{n}}=0, \mathrm{~d}=?$ $a_{n}=a+(n-1) d$ $0=-18+(10-1) d$ $18=9 d \quad \Rightarrow d=\frac{18}{9}=2$ Hence, $d=2$ (iii) $d=-3, n=18, a_{n}=-...
Read More →What do you mean by significant figures
[question] Question. What do you mean by significant figures [/question] [solution] Solution: Significant figures are those meaningful digits that are known with certainty. They indicate uncertainty in an experiment or calculated value. For example, if 15.6 mL is the result of an experiment, then 15 is certain while 6 is uncertain, and the total number of significant figures are 3. Hence, significant figures are defined as the total number of digits in a number including the last digit that repr...
Read More →Find out what do the terms ‘algal bloom’ and ‘red-tides’ signify.
[question] Question. Find out what do the terms ‘algal bloom’ and ‘red-tides’ signify. [question] [solution] Solution: Algal bloom Algal bloom refers to an increase in the population of algae or blue-green algae in water, resulting in discoloration of the water body. This causes an increase in the biological oxygen demand (BOD), resulting in the death of fishes and other aquatic animals. Red-tides Red tides are caused by red dinoflagellates (Gonyaulax) that multiply rapidly. Due to their large n...
Read More →Match the following prefixes with their multiples
[question] Question. Match the following prefixes with their multiples [/question] [solution] Solution: [/solution]...
Read More →Look at the graphs (a) to (d) (Fig. 3.20) carefully and state,
[question] Question. Look at the graphs (a) to (d) (Fig. 3.20) carefully and state, with reasons, which of these cannot possibly represent one-dimensional motion of a particle. [/question] [solution] solution: (a) The given $x-t$ graph, shown in (a), does not represent one-dimensional motion of the particle. This is because a particle cannot have two positions at the same instant of time. (b) The given $v-t$ graph, shown in (b), does not represent one-dimensional motion of the particle. This is ...
Read More →What is the nature of cell-walls in diatoms?
[question] Question. What is the nature of cell-walls in diatoms? [/question] [solution] Solution: The cell walls of diatoms are made of silica. Their cell wall construction is known as frustule. It consists of two thin overlapping shells that fit into each other such as a soap box. When the diatoms die, the silica in their cell walls gets deposited in the form of diatomaceous earth. This diatomaceous earth is very soft and quite inert. It is used in filtration of oils, sugars, and for other ind...
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