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Recent questions tagged ch-8
ASK
(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) ?
cbse
class12
chemistry
sec-e
ch-8
d-and-f-block-elements
asked
Dec 29, 2016
by
sharmaaparna1
1
answer
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.
cbse
class12
chemistry
sec-d
ch-8
d-and-f-block-elements
asked
Nov 29, 2016
by
meena.p
1
answer
(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
cbse
class12
chemistry
sec-e
ch-8
d-and-f-block-elements
asked
Nov 29, 2016
by
meena.p
1
answer
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
cbse
class12
chemistry
sec-e
ch-8
d-and-f-block-elements
asked
Nov 22, 2016
by
meena.p
1
answer
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.
cbse
class12
chemistry
sec-e
ch-8
d-and-f-block-elements
asked
Nov 10, 2016
by
meena.p
1
answer
(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 $513\;K$.
cbse
class12
chemistry
sec-e
ch-8
d-and-f-block-elements
asked
Nov 10, 2016
by
meena.p
1
answer
(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
cbse
class12
chemistry
sec-e
ch-8
d-and-f-block-elements
asked
Nov 8, 2016
by
meena.p
1
answer
Why do the d-block elements exhibits a large number of oxidation states than f - block elements
cbse
class12
chemistry
sec-c
ch-8
d-and-f-block-elements
asked
Nov 3, 2016
by
meena.p
1
answer
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 .
cbse
class12
chemistry
sec-c
ch-8
d-and-f-block-elements
asked
Nov 1, 2016
by
meena.p
1
answer
The second and third rows of transition elements resemble each other much more than they resemble the first row. explain why ?
cbse
class12
chemistry
sec-c
ch-8
d-and-f-block-elements
asked
Oct 24, 2016
by
meena.p
1
answer
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
cbse
class12
chemistry
sec-e
ch-8
d-and-f-block-elements
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
cbse
class12
chemistry
sec-e
ch-8
d-and-f-block-elements
asked
Oct 18, 2016
by
meena.p
1
answer
Why do the d - block elements exhibit a large number of oxidation states than f- block elements
cbse
class12
chemistry
ch-8
sec-c
d-and-f-block-elements
asked
Oct 17, 2016
by
meena.p
1
answer
The diagonal of a rhombus are
olympiad
class8
math
ch-8
mensuration
asked
Jun 20, 2015
by
meena.p
1
answer
Which of the following shape has two dimensions?
olympiad
class8
math
ch-8
mensuration
asked
Jun 20, 2015
by
meena.p
1
answer
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.
olympiad
class8
math
ch-8
mensuration
asked
Jun 20, 2015
by
meena.p
1
answer
Find the surface area of a chalk box whose length , breadth and height are $16\;cm,8\;cm,and 6\;cm$ respectively
olympiad
class8
math
ch-8
mensuration
asked
Jun 20, 2015
by
meena.p
1
answer
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
olympiad
class8
math
ch-8
mensuration
asked
Jun 20, 2015
by
meena.p
1
answer
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 .
olympiad
class8
math
ch-8
mensuration
asked
Jun 20, 2015
by
meena.p
1
answer
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
olympiad
class8
math
ch-8
mensuration
asked
Jun 20, 2015
by
meena.p
1
answer
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.
olympiad
class8
math
ch-8
mensuration
asked
Jun 20, 2015
by
meena.p
1
answer
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 $25\;cm \times 11.25\;cm \times 6\;cm$?
olympiad
class8
math
ch-8
mensuration
asked
Jun 18, 2015
by
meena.p
1
answer
Find the volume of a cube whose total surface area is $384\;cm^2$
olympiad
class8
math
ch-8
mensuration
asked
Jun 18, 2015
by
meena.p
1
answer
What is the volume of a sphere whose radius is $3\;cm$
olympiad
class8
math
ch-8
mensuration
asked
Jun 18, 2015
by
meena.p
1
answer
What is the lateral surface area of a cube of side $5\;cm$
olympiad
class8
math
ch-8
mensuration
asked
Jun 18, 2015
by
meena.p
1
answer
What is the total surface area of a cuibord of dimensions $4\;cm,5\;cm$ and $6\;cm$
olympiad
class8
math
ch-8
mensuration
asked
Jun 18, 2015
by
meena.p
1
answer
If each side of an equilateral triangle is doubled , then its area becomes how many times.
olympiad
class8
math
ch-8
mensuration
asked
Jun 18, 2015
by
meena.p
1
answer
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
olympiad
class8
math
ch-8
mensuration
asked
Jun 18, 2015
by
meena.p
1
answer
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?
olympiad
class8
math
ch-8
mensuration
asked
Jun 18, 2015
by
meena.p
1
answer
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 $2800\;cm^2$
olympiad
class8
math
ch-8
mensuration
asked
Jun 18, 2015
by
meena.p
1
answer
If the diagonal and the area of a rectangle are $25\;m$ and $168\;m^2$, what is the length of the rectangle ?
olympiad
class8
math
ch-8
mensuration
asked
Jun 18, 2015
by
meena.p
1
answer
What is the area of a rhombus whose diagonals are lengths $10\;cm$ and $8.2\;cm$
olympiad
class8
math
ch-8
mensuration
asked
Jun 18, 2015
by
meena.p
1
answer
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 .
olympiad
class8
math
ch-8
mensuration
asked
Jun 18, 2015
by
meena.p
1
answer
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 .
olympiad
class8
math
ch-8
mensuration
asked
Jun 18, 2015
by
meena.p
1
answer
Find the cost of digging a well 2m in radius and 14 m deep at the rate of $Rs. 1.20\;cm^3$
olympiad
class8
math
ch-8
mensuration
asked
Jun 18, 2015
by
meena.p
1
answer
Find the volume of a right circular cylinder whose height and radius of the base are $20\;cm$ and $14 \;cm$ respectively.
olympiad
class8
math
ch-8
mensuration
asked
Jun 18, 2015
by
meena.p
1
answer
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.
olympiad
class8
math
ch-8
mensuration
asked
Jun 18, 2015
by
meena.p
1
answer
Find the diagonal of a cubord $25\;cm$ long , $20\;cm$ wide and $15\;cm$ high.
olympiad
class8
math
ch-8
mensuration
asked
Jun 18, 2015
by
meena.p
1
answer
The diagonal of a cube is $6 \sqrt{3}\;cm$. Find its volume
olympiad
class8
math
ch-8
mensuration
asked
Jun 18, 2015
by
meena.p
1
answer
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 .
olympiad
class8
math
ch-8
mensuration
asked
Jun 18, 2015
by
meena.p
1
answer
Find the total surface area of a cubord whose length $= 5\;m, $breath $=3\;m$ and height $=2.5\;m$
olympiad
class8
math
ch-8
mensuration
asked
Jun 18, 2015
by
meena.p
1
answer
The T.S.A of a cube is $384 \;cm^2$ Find its volume
olympiad
class8
math
ch-8
mensuration
asked
Jun 17, 2015
by
meena.p
1
answer
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.
olympiad
class8
math
ch-8
mensuration
asked
Jun 17, 2015
by
meena.p
1
answer
The line joining the center of the two circles is called ________ of the cylinder .
olympiad
class8
math
ch-8
mensuration
asked
Jun 17, 2015
by
meena.p
1
answer
Find the height of a cubord whose base area is $180\;cm^2$ and volume is $900\;cm^3$
olympiad
class8
math
ch-8
mensuration
asked
Jun 17, 2015
by
meena.p
1
answer
Find the side of a cube whose surface area is $600\;cm^2$
olympiad
class8
math
ch-8
mensuration
asked
Jun 17, 2015
by
meena.p
1
answer
If each side of a cube is doubled its volume becomes _________
olympiad
class8
math
ch-8
mensuration
asked
Jun 17, 2015
by
meena.p
1
answer
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 ?
olympiad
class8
math
ch-8
mensuration
asked
Jun 17, 2015
by
meena.p
1
answer
The length of a rectangle is increased by $60\%$ . By what should the width be decreased to maintain the same area ?
olympiad
class8
math
ch-8
mensuration
asked
Jun 17, 2015
by
meena.p
1
answer
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 $1\;gm$
olympiad
class8
math
ch-8
mensuration
asked
Jun 17, 2015
by
meena.p
1
answer
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