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A substance X, which is an oxide of a group 2 element is used intensively in the cement industry
|
|
1
|
11582
|
July 4, 2016
|
|
Zinc liberates hydrogen gas when reacted with dilute hydrochloric acid, whereas copper does not. Explain, why?
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|
0
|
11562
|
July 4, 2016
|
|
Why is photosynthesis considered an endothermic reaction?
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|
0
|
14409
|
July 4, 2016
|
|
In a school laboratory, a student wants to study the effect of heat on the ferrous sulphate crystals in a boiling tube. State the conclusion he is likely to draw on the basis of his observations
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|
0
|
3454
|
July 4, 2016
|
|
Which reactions below are oxidation?
|
|
1
|
1404
|
July 4, 2016
|
|
In an experiment, solid calcium oxide was taken in a container and water was added slowly to it
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|
1
|
3956
|
July 4, 2016
|
|
A metal salt MX when exposed to light, split up to form metal M and a gas X2. Metal M is used in making ornaments whereas gas X2 is used in making bleaching powder. The salt MX is itself used in black and white photography. (i) Identify metal M and gas X2
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|
1
|
6836
|
July 4, 2016
|
|
Bhawna took a pale green substance A in a test tube and heated it over the flame of a burner. A brown coloured residue B was formed along with the evolution of two gases with burning smell of sulphur. Identify A and B. Write the chemical reaction involved
|
|
0
|
11531
|
July 4, 2016
|
|
Why do we store silver chloride in dark coloured bottles?
|
|
0
|
22965
|
July 4, 2016
|
|
Why do fire flies glow at night?
|
|
0
|
17016
|
July 4, 2016
|
|
Identify the oxidising agents (oxidants) in the following reactions:
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|
1
|
807
|
July 4, 2016
|
|
When the powder of a common metal is heated in an open China dish, its colour turns black. However, when hydrogen is passed over the hot black substance so formed, it regains its original colour. Based on the given information, answer the following
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|
1
|
10752
|
July 4, 2016
|
|
Translate the following reactions into balanced chemical equations: (i) Manganese dioxide is heated with aluminium powder. (ii) Iron is treated with steam
|
|
0
|
4247
|
July 4, 2016
|
|
Using a suitable chemical equation, justify that some chemical reactions are determined by (i) change in colour. (ii) change in temperature
|
|
0
|
7206
|
July 4, 2016
|
|
Define Avogadro's constant. How is it related to mole?
|
|
0
|
3942
|
June 29, 2016
|
|
What is the difference between cation and an anion?
|
|
0
|
2967
|
June 29, 2016
|
|
(i) Name the body which approves the nomenclature of elements and compounds. (ii) The symbol of sodium is written as Na and not as S. Give reason. (iii) Name one element which forms diatomic and one which forms tetraatomic molecules
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|
0
|
3718
|
June 29, 2016
|
|
(a) Define atomicity. (b) Give an example for an element which is monoatomic and a polyatomic molecule
|
|
0
|
2169
|
June 29, 2016
|
|
Mention the two postulates of Dalton’s Atomic Theory that explain: (a) Law of Conservation of Mass (b) Law of Constant Proportions
|
|
0
|
3183
|
June 29, 2016
|
|
(a) What is the law of constant proportions ? Explain with the help of an example. (b) Which postulate of Dalton's atomic theory is in agreement with this law?
|
|
0
|
1338
|
June 29, 2016
|
|
Calculate the number of moles in 5.75 g of sodium (atomic mass of sodium - 23)
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|
0
|
4250
|
June 29, 2016
|
|
(a) What are polyatomic ions ? (b) Write the formulae and names of the compounds formed by combination of:
|
|
0
|
1241
|
June 30, 2016
|
|
Which amongst the following has more number of atoms, 11.5 g of sodium or 15 g of calcium ? How?
|
|
0
|
7433
|
June 30, 2016
|
|
What is the mass of one mole of oxygen atoms ? Convert 12 g of oxygen gas into mole
|
|
0
|
1378
|
June 30, 2016
|
|
What is the difference between an atom and a molecule?
|
|
0
|
658
|
June 30, 2016
|
|
(a) Write chemical formulae of sodium sulphate. (b) Name one element each which forms diatomic and tetraatomic molecule
|
|
0
|
817
|
June 30, 2016
|
|
State thepostulate of Dalton's atomic theory which led to the law of conservation of mass. Calculate the molecular mass of water
|
|
0
|
728
|
June 30, 2016
|
|
Differentiate between: (i) Atom and molecule. (ii) Molecular mass and formula unit mass
|
|
0
|
623
|
June 30, 2016
|
|
Calculate the number of particles in each of the following: (a) 48 g of Mg (b) 8 g of O2 (c) 0.1 mole of carbon (Atomic mass Mg = 24 u, O = 16 u, C = 12 u, Avogadro constant (NA = 6.022 x 10^23)
|
|
0
|
9804
|
June 30, 2016
|
|
Calculate the following quantities in 5.6 g of nitrogen (Atomic mass of N =14u) : (a) Number of moles of N2. (b) Number of molecules of N2. (c) Number of atoms of nitrogen
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|
0
|
8795
|
June 30, 2016
|