Recent questions tagged ch-8

(a) The actinoids exhibit more number of oxidation states and give their common oxidation states. (b)A wellknown orange crystalline compound (A) when burnt impart violet colour to flame. (A) on treating (B) and conc. $H_2SO_4$ gives red gas (C) which gives red yellow solution (D) with alkaline water. (D) on treating with acetic acid and lead acetate gives yellow p. pt. (E). (B) sublimes on heating. Also on heating (B) with NaOH gas (F) is formed which gives white fumes with HCl. What are (A) to (F) ?

asked Dec 29, 2016 by sharmaaparna1

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The chemistry of the actinoid elements is not so smooth as that of the Lanthanoids. Justify this statement by giving some examples from the oxidation state of these elements.

asked Nov 29, 2016 by meena.p

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(i) Why are complexes of the d-block elements coloured ? (ii) Why are scandium and Zinc not counted as transition metals even though they belong to the d-block? (iii)When a brown compound of manganers (A) is treated with $Hcl$ it gives a gas (B) . The gas taken in excess , reacts with $Nh_3$ to give an explosive compound A and B

asked Nov 29, 2016 by meena.p

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Assign reasons for the following: (i) The enthalpies of atomisation of transition elements are high. (ii) The transition metals and many of their compounds act as good catalysts. (iii) From element to element the actinoid contraction is greater than the lanthanoid contraction. (iv) The $E^{\circ}$ value for the $Mn ^{3+} / Mn ^{2+}$ couple is much more positive than that of $Cr^{3+} / Cr^{2+}.$ (v) Scandium $(z=21)$ does not exhibit variable oxidation states and yet it is regarded as a transition element

asked Nov 22, 2016 by meena.p

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Account for the following: i)Fluorine does no show variable oxidation states while other members of the halogen family exhibit variable oxidation states. ii)Iodine is more soluble in $KI$ solution than in water. iii)Why do boiling points of noble gases increases down the group? iv)Why ammonia is a good complexing agent? v)Nitric oxide(NO) is a colourless gas becomes brown when released in air.

asked Nov 10, 2016 by meena.p

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(a) Compare non transition and transition elements on the basis of their (i) Variability of oxidation states (ii) stability of oxidation states. (b) Give chemical reactions for the following observations: (i) Potassium permanganate is a good oxidising agent in basic medium. (ii) Inter convertibility of chromate ion and dichromate ion in aqueous solution depends Upon pH of the solution. (iii) Potassium permanganate is thermally unstable at $513\;K$.

asked Nov 10, 2016 by meena.p

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(a)Draw the molecular structure of the following compounds : $(i)N_2O_5 (ii) X_eOF_4$ (b) Why do the d-block elements exhibits a large number of oxidation states than f - block elements

asked Nov 8, 2016 by meena.p

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Why do the d-block elements exhibits a large number of oxidation states than f - block elements

asked Nov 3, 2016 by meena.p

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How would you account for the following ? (i) Many of the transition elements are known to form interstitial compounds . (ii) The metallic radii of the third (5d) series of transition metals are virtually the same as those of the corresponding group members of the second (4d) series .(iii) Lanthanoids form primary +3 ions , while the actinoids usually have higher oxidation state in their compounds , +4 or even +6 typical .

asked Nov 1, 2016 by meena.p

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The second and third rows of transition elements resemble each other much more than they resemble the first row. explain why ?

asked Oct 24, 2016 by meena.p

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Give chemical reactions for the following observations: (i) Potassium permanganate is a good oxidising agent in basic medium. (ii) Inter-convertibility of chromate ion and dichromate ion in aqueous solution depends upon pH of the solution . (iii) Potassium permanganate is thermally unstable at 513 K

asked Oct 24, 2016 by meena.p

1 answer

(A)(a) Compare non transition and transition elements on the basis of their (i) Variability of oxidation states (ii) stability of oxidation states. (b) Give chemical reactions for the following observations: (i) Potassium permanganate is a good oxidising agent in basic medium. (ii) Inter convertibility of chromate ion and dichromate ion in aqueous solution depends Upon pH of the solution. (iii) Potassium permanganate is thermally unstable at $513\;K$. (B) Why do the d - block elements exhibit a large number of oxidation states than f- block elements

asked Oct 18, 2016 by meena.p

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Why do the d - block elements exhibit a large number of oxidation states than f- block elements

asked Oct 17, 2016 by meena.p

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The diagonal of a rhombus are

asked Jun 20, 2015 by meena.p

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Which of the following shape has two dimensions?

asked Jun 20, 2015 by meena.p

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The dimensions of a cubord are in the ratio of $1:2: 3$ and its total surface are is $88 \;m^2$ Find its dimensions.

asked Jun 20, 2015 by meena.p

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Find the surface area of a chalk box whose length , breadth and height are $16\;cm,8\;cm,and 6\;cm$ respectively

asked Jun 20, 2015 by meena.p

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PQRS is a quadrilateral in which $PQ= 4\;cm; QR= 9.2\;cm;Rs=8\;cm; SP= 6\;cm; \angle {PSR} =\angle {PQR} =90^{\circ}$ Find its area

asked Jun 20, 2015 by meena.p

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A rectangular piece of paper of dimensions $22\;cm$ by $12\;cm$ is rolled along its length to form a cylinder. Find the volume of the cylinder so formed .

asked Jun 20, 2015 by meena.p

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An open rectangular custern when measured outside is $1.35\;m$ long $1.08\;m$ broad and $90\;cm$ deep and is made of iron which is $2.5\;cm$ thick . Find the capacity of the custern and the volume of the iron used

asked Jun 20, 2015 by meena.p

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A field is $80\;cm$ long and $50\;cm$ broad . In one corner of the field , a pit . Which is 10 cm long , $7.5 \;m$ broad and 8 m deep has been dug out. The earth taken out of it is even by spread over the remaining part of the field. Find the ruse in the ;level of the field.

asked Jun 20, 2015 by meena.p

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How many bricks will be required for a wall which is $8\;m$ long $6\;m$ high and $22.5 \;cm$ thick if each bricks measures $25\;cm \times 11.25\;cm \times 6\;cm$?

asked Jun 18, 2015 by meena.p

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Find the volume of a cube whose total surface area is $384\;cm^2$

asked Jun 18, 2015 by meena.p

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What is the volume of a sphere whose radius is $3\;cm$

asked Jun 18, 2015 by meena.p

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What is the lateral surface area of a cube of side $5\;cm$

asked Jun 18, 2015 by meena.p

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What is the total surface area of a cuibord of dimensions $4\;cm,5\;cm$ and $6\;cm$

asked Jun 18, 2015 by meena.p

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If each side of an equilateral triangle is doubled , then its area becomes how many times.

asked Jun 18, 2015 by meena.p

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The area of a rhombus is $240 \;cm^2$ If one of its diagonals is $16\;cm$. What the length of its other diagonal is

asked Jun 18, 2015 by meena.p

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The area of three adjacent faces of cubord are $180 \;cm,96\;cm^2$ and $120\;cm^2$. What is the volume of the cubord?

asked Jun 18, 2015 by meena.p

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A following has a shape of a parallelogram Whose box is $28\;cm$ and the corresponding height is $20\;cm$ how many such tiles are required to cover a floor of a area $2800\;cm^2$

asked Jun 18, 2015 by meena.p

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If the diagonal and the area of a rectangle are $25\;m$ and $168\;m^2$, what is the length of the rectangle ?

asked Jun 18, 2015 by meena.p

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What is the area of a rhombus whose diagonals are lengths $10\;cm$ and $8.2\;cm$

asked Jun 18, 2015 by meena.p

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The area of a trapezium is $352\;cm^2$ The distance between parallel sides is $ 16\;cm$ . If one of the parallel sides is $ 25\;cm$ Find the other .

asked Jun 18, 2015 by meena.p

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The circumference of the base of a right circular cylinder is $88\;cm$ . If the height is $42\;cm$. Find the volume of the cylinder .

asked Jun 18, 2015 by meena.p

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Find the cost of digging a well 2m in radius and 14 m deep at the rate of $Rs. 1.20\;cm^3$

asked Jun 18, 2015 by meena.p

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Find the volume of a right circular cylinder whose height and radius of the base are $20\;cm$ and $14 \;cm$ respectively.

asked Jun 18, 2015 by meena.p

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A granary is in the shape of a cubord of size $8\;m \times 6\;m \times 3\;m$ If a bag of grain occupies a space of $0.65\;m^3$ haw many bags can be stored in the granuary.

asked Jun 18, 2015 by meena.p

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Find the diagonal of a cubord $25\;cm$ long , $20\;cm$ wide and $15\;cm$ high.

asked Jun 18, 2015 by meena.p

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The diagonal of a cube is $6 \sqrt{3}\;cm$. Find its volume

asked Jun 18, 2015 by meena.p

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A cubord measures $80\;cm \times 75\;cm \times 36\;cm$ . It is melted and a cube is formed. Find the edge of the cube .

asked Jun 18, 2015 by meena.p

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Find the total surface area of a cubord whose length $= 5\;m, $breath $=3\;m$ and height $=2.5\;m$

asked Jun 18, 2015 by meena.p

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The T.S.A of a cube is $384 \;cm^2$ Find its volume

asked Jun 17, 2015 by meena.p

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A parallelogram and rhombus are equal in area . The diagonals of the rhombus $48\;cm$ and $36\;cm$ . If one of the sides of the parallelogram is $4\;cm$ . find its corresponding altitude.

asked Jun 17, 2015 by meena.p

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The line joining the center of the two circles is called ________ of the cylinder .

asked Jun 17, 2015 by meena.p

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Find the height of a cubord whose base area is $180\;cm^2$ and volume is $900\;cm^3$

asked Jun 17, 2015 by meena.p

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Find the side of a cube whose surface area is $600\;cm^2$

asked Jun 17, 2015 by meena.p

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If each side of a cube is doubled its volume becomes _________

asked Jun 17, 2015 by meena.p

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The diagonal of the floor of a rectangle is increased by $60\%$ . By what percentage should the width be decreased to maintain the same area ?

asked Jun 17, 2015 by meena.p

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The length of a rectangle is increased by $60\%$ . By what should the width be decreased to maintain the same area ?

asked Jun 17, 2015 by meena.p

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A rectangular block of ice measures $40\;cm$ by $25\;cm$. by $15\;cm$ . calculate its weight in kg , if ice weight $\large\frac{9}{10}$ of the weight of the same volume of water and $10\;cm^3$ of water weights $1\;gm$

asked Jun 17, 2015 by meena.p

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