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SCI - CLASS 10 (CBSE) > Chp- 1 Chemical Reactions And Equations > Flashcards

Chp- 1 Chemical Reactions And Equations Flashcards

1
Q

Why do we need to rub a magnesium ribbon with sandpaper before using it for experimentation?

A

Magnesium metal has a shining surface but due to the attack of moist air it is coated with a white layer of magnesium oxide therefore in order to use it for any chemical reaction it is first rubbed with a sandpaper

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2
Q

True or false -

Magnesium ribbon burns with a dazzling golden yellow flame and changes into white powder called manganese oxide

A

False; Magnesium ribbon burns with a dazzling white flame and changes into white powder called magnesium oxide.
On the other hand sodium burns with a golden flame and potassium with lilac colour flame.

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3
Q

What are the factors on which we can determine whether there has been a chemical reaction or not.

A

Change in state
- Formation of solid magnesium oxide from solid magnesium and gaseous oxygen

change in colour

  • Formation of yellow precipitate of lead iodide from a colourless solution of Lead nitrate and potassium iodide
  • When citric acid reacts with potassium permanganate solution then the purple colour of the potassium permanganate solution KMnO4 disappears that is it becomes colourless.
  • When sulphur dioxide gas is passed through potassium dichromate( K2 Cr2O7) solution, the orange colour of potassium dichromate changes to green

evolution of gas

  • Evolution of H2 gas in the reaction of the zinc and the dil hydrochloric acid
  • 2HCL+ Na2CO3——-> 2NaCl+ H2O + CO2

change in temperature
- In the reaction of barium hydroxide and ammonium chloride it is observed that the bottom of the test-tube is cool (endo)
Ba(OH)2 + 2NH4Cl → BaCl2 + 2NH3 + 2H2O
- When quicklime reacts with water then slaked lime is formed and a lot of heat energy is produced

formation of precipitate

  • Formation of yellow precipitate of lead iodide from a colourless solution of Lead nitrate and potassium iodide
  • BaCl+ H2SO4 ——> BaSO4(white ppt) + HCL
  • Ca(OH)2 + CO2 ——> CaCO3 (wht ppt) + H2O
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4
Q

Define reactants and the product

A

The substances that undergo chemical change in the reaction are called reactants. While on the other hand can use substance formed during the reaction is called product .

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5
Q

What is the skeletal chemical equation

A

Skeletal chemical equation is a representation of a chemical reaction using chemical formulae of reactants and products. In skeletal chemical equation the mass no of elements in reactant side is not equal to the mass no of elements in product side.

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6
Q

What law do we follow while balancing the chemical equation

A

Law of conservation of mass that states that mass can neither be created nor destroyed in a chemical reaction

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7
Q

What are the characteristics features of physical changes

A

The identity of the substance is maintained
change is temporary
Heat change may or may not take place
only physical state or some physical properties are changed

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8
Q

What are the characteristic features of chemical changes

A

The identity of the original substance is completely lost

the change is generally permanent

change is generally accompanied by energy

change the change cannot be reversed

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9
Q

Define precipitate and how can it be formed

A

Precipitate is an insoluble solid that forms out of a liquid solution that does not dissolve in the solution.
A precipitate can be formed by mixing aquaeous solution of reactants when one of the products is insoluble in water. A pacific it can also be formed by passing a gas into an aqueous solution of a substance. Like passing carbon dioxide into limewater

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10
Q

What is stoichiometric Coefficient

A

In a balanced equation an integer precedes the formula of each substance this number is called stoichiometric coefficient.( stoy. Kee. Ow. Meh. Truhk)

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11
Q

What is hit and trial method?

A

The method of balancing the equation by using the smallest natural number is called hit and trial method

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12
Q

What are the. Magnetic oxides of iron

A

The mixture of ferrous oxide and ferric oxide is called magnetic oxide of iron

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13
Q

How woyld you represent steam in symbolic details

A

the symbol g )is used with H20 to indicate that the water is used in the form of steam

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14
Q

What is Combination reaction? Give eg.

A

between two or more compounds

Combination reaction also called addition reaction or synthesis reaction is a reaction in which two or more substances combine to form a single new substance.
Combination reaction can take place between:-
#two or more elements
• Fe(s) + S(s) ——-(heat)——> FeS
Iron sulphide.

• CaO(s) + CO2(g) ———> CaCO3 (s)
(Quick lime)

 #between elements and compounds
• 2 NO(g) + O2 (g) ———> 2NO2(g)
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15
Q

True or false -

Zinc oxide is yellow in colour when cold and white when hot

A

False ; ZnO changes it colour on heating it is yellow when hot and white when cold

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16
Q

Explain why is respiration exothermic reaction?

A

The food that we eat provides the energy to stay alive. during Digestion, Food is broken down into simpler substances. for example, rice potatoes and bread contain carbohydrates- these carbohydrates are broken down to form glucose. this glucose undergoes slow combustion by combining with oxygen in the cells of the body and provides us energy. this process is respiration. Since the energy which maintains our body heat is liberated we can say that respiration is an exothermic reaction

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17
Q

True or False -

Combination reactions are usually endothermic in nature

A

False; Combination reactions are usually exothermic in nature

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18
Q

True or false -

The decomposition of vegetable matter into compost is example of exothermic reaction

A

True.

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19
Q

Fill in the blanks -
Calcium oxide which is also called ______ reacts vigourously with water to produce ______ which is also called ________ releasing a large amount of heat

A

1) Quick lime
2) Calcium hydroxide
3) Slaked lime

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20
Q

True or False-

The chemical formula of Marble is CaCO2

A

False; The chemical formula is CaCO3

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21
Q

the solution of X is used for white washing walls. This X reacts slowly with Y present in the air to form a thin layer of Z giving finish to the walls. The chemical formula of A and Z is same.
FIND X,Y,Z,A

A

X- slaked lime/ Calcium hydroxide
Y- Carbon dioxide
Z- calcium carbonate
A- Marble

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22
Q

Fill in the blanks -
The Colour of copper sulphate ‘solution’ is____ .
While the colour of crystalline ferrous sulphate before and after heating is _______ and _______ respectively.

A

1) CuSO4 solution - blue
2) FeSO4 - before heating - light green

3) FeSO4 -after heating - White

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23
Q

How do you test the presence of hydrogen

A

By bringing a lit candle near the gas evolved.

24
Q

Give the Equation of the reaction between Zinc and sulphuric acid

A

Zn(s) + H2SO4 —–> ZnSO4 +H2 +heat

25
Q

Give the Equation for the reaction of zinc granules and NaCL, NaOH

A

No reaction takes place because sodium is more reactive than zinc. Zinc cannot displace sodium.

26
Q

What is a biochemical reaction?

A

A biochemical reaction is the transformation of one molecule to different molecules inside a cell for example respiration, digestion , etc

27
Q

What is the decomposition reaction.

A

The reaction in which a single compound breaks up into two or more simpler substances is called decomposition reaction. Decomposition reaction generally takes place when energy in some form such as heat electricity or light is supplied to the reactants.

28
Q

Define thermal decomposition with an

A

The decomposition reaction in which absorption of heat takes place is called thermal decomposition reaction
For example
2FeSO4.7H2O+ heat—-> Fe2O3(s) +SO2 + SO3
(Ferrous sulphate (Brown) (smell of Heptahydrate.(green) burning sulphur)
Where is sulphate crystals lose water when heated and colour changes to white. It then decomposes to ferric oxide, Sulphur dioxide and sulphur trioxide

CaCO3 —heat—> CaO+ CO2
2 KCLO3 ——heat—-> 2KCL+3O2
k Chlorate

29
Q

What happens when you heat lead nitrate

A

2Pb(NO3)2—heat—>2PbO+4NO2 + O2
(colourles (Yellow) (brown fumes)
When heat lead nitrate in powder form we get solid lead oxide, brown fumes of nitrogen dioxide and O2

Note- Lead monoxide is reddish brown when hot and yellow when cold

30
Q

what is red lead

A

PbO is used in manufacture o f fine crystal glass. One part of PbO2 Mixed with two parts of PBO is called Pb3O4. This is called.
Red lead or sindoor

31
Q

Why is the volume of gas collected during the electrolysis of water different in both the test tubes

A

The volume of gas collected at cathod is double than that at anode. At cathode hydrogen is present And at anode oxygen is present. Both of them can we b checked by bringing a lit candle near. If there is a pop sound it is hydrogen and if the flame starts Glowing brighter

32
Q

What is electrolytic Decomposition. Give few examples

A

The kind of reaction in which electric current is passed through the compound in liquid or aqueous solution Called electrolytic decomposition

2NaCl —electric current- 2Na +Cl2

2Al2O3 -electric current- 4Al +. 3 O2
Alumina (molten)

33
Q

What is photo lysis. Give few examples

A

The type of reaction which takes place on absorption of light are called photo decomposition reaction.
2AgCl(s)-sunlight—> 2Ag. + Cl2
(white). (Grey). (Greenish yellow

2AgBr—-sunlight—-> 2Ag. + Br2
(Pale Yellow) (Grey). (Reddish brown)

2H2O2 ————light—> 2H2O + O2(g)
(hydrogen peroxide)

34
Q

Fill in the blank

Photo lysis of a _____ is used in black and white photography

A

AgBr

35
Q

Why is oxygen liberated during the process of photosynthesis

A

photolysis of water

36
Q

Why is hydrogen peroxide kept in amber coloured bottles

A

to cut it off light

37
Q

What is displacement reaction give a few examples

A

The reaction in which a more reactive element displaces a less reactive element from its compound is called displacement reaction. The elements involved maybe metals or non-metals.
Fe+ CuSO4 (aq)——> FeSO4 +. Cu
(Blue). (Lt. Green)

2Na+. 2 H2O —-> 2NaOH+ H2
(silvery wht). (Colourless)

Cu+ 2AgNO3—> CuNO3)2 + 2 Ag
(Colourless). (Blue)

CuCl2 + Pb -————> PbCl2 + Cu
(Green)(Bluish grey. (Colourless)

Fe2 O3 + 2Al ——> Al2 O3 + 2Fe
So much Heat is produced that the iron is obtained in molten state

38
Q

Define double displacement reaction with a few examples

A

The reaction in which different atoms or group of atoms are exchanged. In this exchange of ions between the reactants takes place. It generally takes place between two ionic compounds:
•AgNO3 + NaCl —> AgCl(wht ppt) + NaNO3(aq)

  • CuSO4 + 2NH4OH—-> Cu(OH)2( bluish white ppt) + 3(NH4)2SO4
  • BaCl2 + Na2SO4 ——> NaCl + BaSO4(white ppt)
  • BaCl2 + CuSO4 —-> BaSO4 (white ppt)+ CuCl2

•CuSO4 + H2S —-> H2SO4 + CuS(black ppt)
The reaction between acid and bases to form salt are double displacement. NaOH + HCL—-> NaCl+ H2O

39
Q

What is Oxidation, Oxidising agent, Reducing agent and give a few examples of REDOX

A

• The reaction which involves the addition of oxygen or removal of hydrogen from a substance is called oxidation reaction.
• Removal of e- or addition of electronegative el(F,O,N,Cl,I)/ non metallic elements is called Oxidation
• Addition of electron or addition of metallic element or removal of non-metallic element is called reductions.
metals - electro+ and non metals elctro-
• Oxidising Agent- Substance that gives oxygen or gains Hydrogen is called oxidising agent. It is a e- accepting species.
The substance that gets oxidised is the reducing agent.
The substance which gets reduced is oxidising agent
•-• CuO + H2 —-> Cu + H2O
•-• H2S + Cl2 —-> S + 2HCL
(Reducing agent : H2S )
•-• ZnO + C —-> Zn + CO
•-• MnO2 + 4 HCL —-> MnCl2 + Cl2 + 2H2O

40
Q

what is oxidising no. and state its rules.

A

Oxidising no- the charge which an atom of element has on its ion or appears to have when present in the combines state with other atoms .
Rules-
•oxidation no of an atom in their free state is 0
oxidation no of O2= 0, p4=O, S8=0
•For ions composed of only 1 Atom, oxidising no. = charge on ion, Fe^3+, no=3
• Oxidation no. Of oxygen in most compounds is -2, except fluorine and peroxide.
• Oxidation no. is H is +1 in compounds except when it bonded with metals.
- Fluorine oxidation no. is always -1.
-The algerbraic sum of all oxidizing no. in a compound should be zero coz compound has no charge.(imp to find charges.. vid check)

41
Q

what is corrosion and give a examples of it.

A

the chemical or electrochemical reaction between a metals, and it s environment( by the action of air/ moisture/ chemical) that produces a deterioration of the metal and its properties is called corrosion. During corrosion metals get converted to metal oxides, sulphide, carbonate, etc.
4Fe +3O2 +xH2O——> 2Fe2O3.xH2O
Rust as a soft and porous substance which gradually fall off from the substance of the iron object and then iron below starts rusting. Thus, rusting of iron is a continuous process which if not prevented and time eats up the whole iron object
2Cu +CO2+H2O-—CuCO3.Cu(OH)2
2Ag + H2S———Ag2S+ H2
Lead or stainless steel loses it lustre due to corrosion.

42
Q

what is Rancidity and how to prevent it?

A

The aerial oxidation of oils n fats in the food marked by bad taste and unpleasant smell is called rancidity. It is caused due to prolonged exposure of food to air.Oxygen present in air oxidises fats/oils present in the food and form volatile substances which have bad odour.
prevention-
1)by adding antioxidants to the food
2)by packaging food and oil containing foods in the presnce of nitrogen.
3)by storing food in refrigerator( less oxidation due to low temperature)
4)by storing food in air tight containers
5) by storing food away from light

43
Q

why do fire flies glow.

A

there is a luminous bag found at thelower abdomen of fire flies. The light emits from this because of secretion of luciferase enzyme. This enzyme when reacts with luciferin, light is emitted because of the presence of mg and o2 due to oxidation of Mg.

44
Q

what are anti oxidants

A

antioxidants are reducing agents which when added to food, the food do not get oxidised easily and hence do not turn rancid easily.
common anti-oxidants-
(A) BHA- butylated Hydroxy Anisole
(B) BHT- butylated Hydroxy Toulene
Vitamin C and Vitamin E are two naturally occuring anti-oxidants

45
Q

What is the shorthand method of representing the composition of a substance

A

A chemical equation is a shorthand way of writing a chemical reaction using chemical symbols, formulas and coefficients. Matter cannot be created or destroyed in a chemical reaction. Atoms are simply rearranged to form new substances. Coefficients are whole numbers placed in front of reactants and products.

46
Q

Why is liquid hydrogen used in space shuttles

A

Liquid Hydrogen bonds reacts with liquid oxygen to formWater, which provide tremendous amount of energy to lift the shuttle out of the earth’s gravitional field.

47
Q

Give examples of endothermic and exothermic reaction

A
  • C+ O2 ——> CO2+ heat
  • CH4 + 2O2 ——> CO2 + 2H2O + heat
  • Decomposition of vegetable matter
  • Respiration

Endothermic

  • Photosynthesis
  • N2(g) + O2 + heat(3000•C) ——> 2NO(g)
  • CaCO3 + heat —-> CaO+ CO2
  • electrolysis of water
48
Q

Give two eq where there is the presence of catyst .

A

2KClO3 ——heat+ MnO2(manganese oxide) —-> 2KCl + 3o2
Potassium chlorate Potassium chloride

CO+ 2H2 —300atm;300•C; ZnO+ CrO3(chromium trioxide)——-> CH3OH( methanol)

49
Q

What happens when

1) sodium metal reacts with water
2) Hydrogen gas combines with nitrogen
3) . Heated iron metal reacts with steam

A

1) Sodium metal reacts with water sodium hydroxide and hydrogen is given out
2Na+ 2H2O—> 2NaOH + H2

When hydrogenGas combines with nitrogen ammonia gas is formed
3H2 + N2 —-> 2NH3

when heated Iron metal reacts with steam to form magnetic iron oxide and hydrogen gas
Fe+ H2O(g)—-> Fe2O3 + H2

50
Q

Why why is photosynthesis endothermic

A

During photosynthesis, carbon dioxide combines with water in the presence of sunlight and a green pigment of leaves called chloroplast to make the food like glucose and oxygen is given out. The conditions for the reaction of photosynthesis to take place in the presence of sunlight and chloro Phil. Since energy is absorbed during the process of photosynthesis and in any chemical reaction that absorbs heat energy from the surrounding to form product is endothermic we call photosynthesis is an endothermic reaction

51
Q

A metal X forms a salt XSO
The salt XSO forms a clear solution in water which reacts with sodium hydroxide solution to form a blue precipitate Y. Metal X is used in making electric wires and alloys like brass
a) What do you think metal X could be?
b) Write the name, formula and colour of salt XSO
c) What is the blue precipitate Y?
d) Write a chemical equation of the reaction which takes place when salt XSO reacts with sodium hydroxide solution. Give the state symbols of all the reactants and products which occur in the above equation.

A

Metal X is Copper (Cu).

b) The name, formula and colour of salt XSO is Copper sulphate, CuSO and blue colour respectively.
c) The blue precipitate Y is Copper hydroxide, [Cu(OH) 2
d) CuSO4 (aq)+2NaOH(aq)→Cu(OH) (s)+Na2SO 4(aq)

52
Q

The metal M reacts vigorously with water to form a solution S and a gas G. The solution S turns red litmus to blue whereas gas G, which is lighter than air, burns with a pop sound. Metal M has a low melting point and it is used as a coolant in nuclear reactors.

(a) What is metal M?
(b) What is solution S? Is it acidic or alkaline?
(c) What is gas G?
(d) Write a balanced chemical equation for the reaction which takes place when metal M reacts with water.
(e) Is this reaction exothermic or endothermic?

A

Metal M is Sodium (Na).

b) Solution S is Sodium hydroxide solution (NaOH solution) and it is alkaline in nature.
c) Gas G is Hydrogen gas
d) 2Na(s)+2H2O(l)→2NaOH(aq)+H 2(g)
e) The reaction is Exothermic in nature as a lot of heat is evolved.

53
Q

When a mixture of gases X and Y is compressed to 300 atm pressure and then passed over a catalyst consisting of a mixture of zinc oxide and chromium oxide (heated to a temperature of 300°C), then an organic compound Z having the molecular formula CH4O is formed. X is a highly poisonous gas which is formed in appreciable amounts when a fuel burns in a limited supply of air ; Y is a gas which can be made by the action of a dilute acid on an active metal; and Z is a liquid organic compound which can react with sodium metal to produce hydrogen gas.

(a) What are X, Y and Z ?
(b) Write a balanced chemical equation of the reaction which takes place when X and Y combine to form Z. Indicate the conditions under which the reaction occurs.

A

A) X is carbon monoxide gas (CO); Y is hydrogen gas (H2) ; Z is methanol (or Methyl alcohol) (CH3OH)
(CH40 = CH3OH)
B) CO+ 2H2 —300atm;300•C; ZnO+ CrO3——-> CH3OH( methanol)
C) The conditions for this reaction to take place are: a pressure of 300 atmospheres (written as 300 atm), a temperature of 300oC, and a catalyst which is a mixture of zinc oxide and chromium oxide (ZnO + CrO3)

54
Q

The white solid compound A decomposes quite rapidly on heating in the presence of a black substance X to form a solid compound B and a gas C. When an aqueous solution of compound B is reacted with silver nitrate solution, then a white precipitate of silver chloride is obtained along with potassium nitrate solution. Gas C does not burn itself but helps burn things.

what is compound A?
What is compound B?
What is gas C?
What do you think is the black substance X? What is its function?
What is the general name of substance like X?

A

a) Potassium chlorate, KClO3
(b) Potassium chloride, KCl
(c) Oxygen, O2
(d) Manganese dioxide, MnO2; It acts as a catalyst in the decomposition of potassium chlorate to form oxygen gas
(e) Catalysts

55
Q

Gas A, which is the major cause of global warming, combines with hydrogen oxide B in nature in the presence of an environmental factor C and a green material D to form a six carbon organic compound E and a gas F. The gas F is necessary for breathing.

A) What is gas A?
What is the common name B?
What do you think could be C?
What is material D? Where is it found?
Name the organic compound E.
What is gas F? Name the natural process during which it is released.
A

a) Carbon dioxide, CO2
(b) Water, H2O
(c) Sunlight.
(d) Chlorophyll; Green leaves of plants.
(e) Glucose, C6H12O6
(f) Oxygen; Photosynthesis.

SCI - CLASS 10 (CBSE) (10 decks)

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