Class 10 Science chapter - 1 Chemical equations and reaction (part -1)

Chemical equations and reaction

MCQ (Multiple Choice Questions)

1. Which of the following reactions involves the combination of two elements :-
a)CaO + CO2 -> CaCO3
b)4Na + O2 -> 2Na2O
c)SO2 +(1/2)O2 -> SO3
d)NH3 + HCI -> NH4CI

2.When hydrogen sulphide gas is passed through a blue solution of copper sulphate, a black precipitate of copper sulphate is obtained and the sulphuric acid so formed remains in the solution. The reaction is an example of :-
a)A combination reaction
b)A displacement reaction
c)A decomposition reaction
d)A double decomposition reaction 

 3.What happens when copper rod is dipped in iron sulphate solution :-
a)Copper displaces iron
b)Blue color of copper sulphate solution is obtained
c)No reaction takes place
d)Reaction is exothermic

 4.A student added dilute HCI to a test tube containing zinc granules and made following observations :-
a)The zinc surface became dull and black
b)A gas evolved which burnt with a pop sound
c)The solution remained colorless
d)The solution becomes green in color.

5.A dilute solution of sodium carbonate was added to two test tubes one containing dilute HCI (a) and the other containing dilute NaOH (b). the correct observation was :-
a)A brown colored gas liberated in test tube A
b)A brown colored gas liberated in test tube B
c)A colorless gas liberated in test tube A
d)A colorless gas liberated in test tube B

6.A balanced chemical equation is in accordance with
a)Avogadro’s law
b)Law of multiple proportion
c)Law of conservation of mass
d)Law of gaseous volumes

7.The equation
Cu + xHNO3 -> Cu(NO3)2 + yNO2 + 2H2O
The values of x and y are
a)3 and 5
b)8 and 6
c)4 and 2
d)7 and 1

8.Zn + H2SO4(dil) ->ZnSO4 + H2 Above reaction is
a)Decomposition reaction
b)Single displacement reaction
c)Combination reaction
d)Synthesis reaction

9.The reaction in which two compounds exchange their ions to form two new compounds is
a)A displacement reaction
b)A decomposition reaction
c)An isomerization reaction
d)A double displacement reaction

10.When the gases sulphur dioxide and hydrogen sulphide mix in the presence of water, the reaction is
SO2 + 2H2S -> 2H2O + 3S. here hydrogen sulphide is acting as
a)An oxidizing agent
b)A reducing agent
c)A dehydrating agent
d)A catalyst

11.CuO + H2 ->H2O + Cu, reaction is an example of
a)Redox reaction
b)Synthesis reaction
c)Neutralization
d)Analysis reaction

12.A substance which oxidized itself and reduces other is known as
a)Oxidizing agent
b)Reducing agent
c)Both of these
d)None of these

13.A redox reaction is one in which
a)Both the substance are reduced
b)Both the substance are oxidized
c)An acid is neutralized by the base
d)One substance is oxidized while the other is reduced

14.In the following equation:
Na2CO3 + xHCI -> 2NaCI +CO2 + H2O, the value of x is
a)1          b)2      c)3             d)4

15.In the equation, NaOH + HNO3 -> NaNO3 + H2O nitric acid is acting as
a)An oxidizing agent
b)An acid
c)A nitrating agent
d)A dehydrating agent

16.Fe2O3+  2Al   ->   AI2O3 + 2Fe
The above reaction is an example of a
a)Combination reaction
b)Double displacement reaction
c)Decomposition reaction
d)Displacement reaction

17.White silver chloride in sunlight turns to
a)Grey
b)Yellow
c)Remain white
d)Red

18.Black and white photography uses
a)Decomposition of silver chloride
b)Decomposition of silver bromide
c)Both
d)None of these

19.When copper powder is heated it gets coated with
a)Black copper oxide
b)Yellow copper oxide
c)Red copper oxide
d)None of these

20.Combination of phosphorus and oxygen is an example of
a)Oxidation
b)Reduction
c)Rancidity
d)None of these

21.Rusting of an iron is an example of
a)Reduction
b)Ionization
c)Oxidation
d)Dissociation

22.Which of the following does not corrode when exposed to the atmosphere-
a)Iron
b)Copper
c)Gold
d)Silver

23.Take about 1.0g CaCO3 in a test tube. Heat it over a flame, when a colorless gas comes out. The reaction is called a
a)Decomposition reaction
b)Displacement reaction
c)Double decomposition reaction
d)Double displacement reaction

24.Hydrogen sulphide (H2S) is a strong reducing agent. Which of the following reactions shows its reducing action
a)Cd(NO3)2 + H2S -> CdS + 2HNO3
b)CuSO4 + H2S -> CuS + H2SO4
c)2FeCl3 + H2S -> 2FeCl2 + 2HCI + S
d)Pb(NO3)2 +H2S -> PbS + 2CH3COOH

25.When P reacts with caustic soda, the products are PH3 and NaH2PO2. This reaction is an example of
a)Oxidation
b)Reduction
c)Oxidation and reduction (redox)
d)Neutralization

26.2CuI-> Cu + CuI2, the reaction is
a)Redox
b)Neutralization
c)Oxidation
d)Reduction

27.When copper turning are added to silver nitrate solution, a blue coloured solution is formed after some time. It is because, copper-
a)Displaces silver from the solution
b)Forms a blue colored complex with AgNO3
c)Is oxidized to Cu2+
d)Is reduced to Cu2+

28.Zn2+ (aq) +2e -> Zn(s). this is
a)Oxidation
b)Reduction
c)Redox reaction
d)None of these
29. The pair of quick lime and slaked lime is 
a. CaO and Ca(OH)2
b. NaOH and KOH
C. CaCl2 and CaSO4
D. CaOCl2 and KCl

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Solution and Colligative properties

Vapour pressure of liquid solution:- 
      when a liquid solution is kept in a closed when a container, some of the molecules of liquid from its surface starts evaporating & start accumulating in the space above the surface of the liquid. due to lesser force of attraction and more kinetic energy present in surface molecule.
     Molecules of liquid in the vapour phase more randomly & strike the liquid surface & get condensed. The process keeps on until equilibrium between evaporation & condensation reached.            
      The pressure exerted by molecules of vapour phase present in the vacant space of the container over the liquid surface is called vapour pressure.
Factors on which vapour pressure of a liquid depends : - 
( a). Nature of the liquid - Each liquid has a characteristics vapour pressure because each liquid has different magnitude of intermolecular forces .
(b). Temperature - The vapour pressure of a liquid increase with increase in temperature. due to increase in kinetic energy of molecules present in liquid(with increase in temperature).
 (c).Boiling point:-vapour pressure is inverse  to boiling point.
(d). Purity of liquid : pure liquid has always higher vapour pressure compare to its solution .
Vapour Pressure of liquid - liquid solutions:- 
                The French chemist, Francois Mate Raoult (1886)gave a quantitative relationship between partial vapour pressure of each component of the solution & its mole fraction.
It states that the vapour pressure of solution is directly proportional to mole faction of a solute added to the solution
Raoult law for volatile liquids: -It states that The partial pressure of each volatile component of the solution is directly proportional to its mole fraction present in solution.
let us consider a binary solution of two volatile liquids denoted as component-1 & 2. Let the total vapour pressure be Ptotal at equilibrium state, p₁ & p₂ be the partial vapour pressure of two components 1 & 2 respectively.
Thus, by applying RaouIt's law for component - 1
               p₁ α  𝝌₁               . . . . . . . . .(i)
                    P₁ = p₁⁰ 𝝌_{1           . . . . . . . . . . . .(ii)}   where p₁⁰ is the vapour pressure of  pure component -1  

similarly for component -2
                   p₂ α  𝝌₂. . . . . . . . .(iii)
                  P₂ = p₂⁰ 𝝌_{2   . . .  . . . .(iv)}       where p₁⁰ is the vapour pressure of  pure component -2
According to Dalton's law of partial pressures-
                                                                            the total pressure (p _total)over the solution phase will be the sum of the partial pressure of the components of the solution.

   p_{total =}  p_{1 +} p_{2  . . . . . . . . . . . . . . . . (v)  
           by} substituting the values of p_{1 &} p_{2 we get} 

    p_total=p₁⁰ 𝝌_1 +  p₂⁰ 𝝌_{2     . . . . . . . . .(vi)                                                                             
             = (1-}𝝌₂₎ p₁⁰₊  p₂⁰ 𝝌_{2  . . . . . . . (vii) Since}  𝝌_1 +  𝝌_{2 = 1
            =}   p₁⁰₊₍ p₂⁰ _- p₁⁰ )𝝌_{2 . . . . . . .(viii)}
for-composition of vapour phase   in equilibrium: 
                 Let  y₁ &  y₂mole fraction and p_1,p₂ partial pressure of the component 1 & 2 respectively in vapour phase.
P₁ =  y₁ p_{total       . . . . . (ix)}          

P₂ =  y₂ p_{total     . . . . . .(x)}

or   y₁₌ p₁/p_total                 y₂₌  p₂ / p_totat 
    y₁= p₁ 𝝌₁⟋p⁰₁ 𝝌_1 +p₂⁰𝝌₂    . . . . . . . ( xi)    
     y₂= p₂ 𝝌₂/p⁰₁ 𝝌_1 +p₂⁰𝝌_{2  . . . . . . . . . xii
eq. ( xi) & (xii) may be used to find out the composition of  in vapour phase.}
Raoults Law for solutions containing solids in liquids: 
 Only liquids are volatile components in solution. So it can evaporate as vapour. Thus thus vapour pressure is due to volatile liquid. 
Raoult's law may state that the partial vapour pressure of volatile component in solution is directly proportional to its mole fraction. 
In mathematics 
   p_vol  α  𝝌_vol
   P_vol = p_vol⁰ 𝝌_{vol 
Solid non volatile does not contribute in vapour pressure, since it does not form vapour.}  

Ideal and non ideal solutions:-

              Ideal solution                                                
 i)  Obey Raoults law P₁ = p₁⁰ 𝝌₁   P₂ = p₂⁰ 𝝌₂  

 ii)  ΔH (mix) = 0            ΔV (mix) = 0 

              non ideal solution     

 i) don't obey raoults law   P₁ # p₁⁰ 𝝌₁    P₂ # p₂⁰ 𝝌₂ 

ii)   ΔH (mix) ≠ 0                    ΔV (mix) ≠ 0

                       

ideal

non ideal solution

Independent For Example, consider two liquids A and B, and mix them. The formed  solution will experience several intermolecular forces of attractions inside it, which will be: A – A intermolecular forces of attraction B – B intermolecular forces of attraction A – B intermolecular forces of attraction The solution is said to be an ideal solution, only  when the intermolecular forces of attraction  between A – A, B – B and A – B are nearly equal. Examples of Ideal Solutions n-hexane and n-heptane Bromoethane and Chloroethane Benzene and Toluene Chlorobenzene and Bromobenzene CCl4 and SiCl4

Interacts with others.                           The solute-solute and solvent-solvent interaction is different from that of solute-solvent interaction Non-ideal solutions are of two types: (a) Non-ideal solutions showing positive deviations:  Positive deviation occurs when total vapour pressure for any mole fraction is more than what is expected according to Raoult’s law. This happens when the new interactions are weaker than the interaction in the pure component (A – B < A – A or B – B interactions). It forms minimum boiling azeotropes, for example, C2H5OH + cyclohexane. The Bonding present in pure C2H5OH is cut off on adding cyclohexane. For such solution, ΔV and ΔH are positive. Examples: Acetone + carbon disulphide, Acetone + benzene Carbon tetrachloride + chloroform or Toluene Methyl alcohol + water Acetone + C2H5OH Non-ideal solutions showing negative deviations:  Negative deviation occurs when total vapour pressure for any mole fraction is less than what is expected according to Raoult’s law. This happens when the new interactions are stronger than the interaction in the pure component (A – B > A – A or B – B interactions). It forms maximum boiling azeotrope, for example, CHCl3+ CH3COCH3.For such solutions, ΔV and ΔH are negative. Examples: Chloroform + benzene or diethyl ether Acetone + aniline Nitric acid (HNO3) + water Acetic acid + pyridine

Solution and Colligative Properties

Chapter - Solution and colligative properties

 In normal life we rarely come across pure substances.
The utility or importance of mixture containing two or more pure substance in life depends on their composition. 

For Example 

• The properties of brass (mixture of Cu & Zn ) are quite different from those of German silver (mixture of Cu, Zn & Ni on Bronze ('mixture of Cu & Sn)
• 1 ppm of fluoride ions in water prevents tooth decay, while 1.5 ppm causes the tooth to become mottled & high concentration of fluoride ions can be poisonous ( for Example , NaF is used in rat poison)
• Binary solution : consisting of two components.

Type of solution
gaseous solution: solvent must be gas  -  Ex. mixture of oxygen and nitrogen gases, camphor in nitrogen gas
liquid solution: solvent must be liquid  - Ex. oxygen dissolved in water, Glucose dissolved in water
solid solution: Solvent must be solid Solution in Hydrogen in palladium, Amalgam of mercury with Sodium, copper dissolved in gold
Expressing Concentration of solution: Composition of a solution can be described by expressing its concentration. There are Several ways by which we can describe the concentration of solution quantitatively.
(1) Mass percentage (w/w) : -It is defined as the part of solute dissolved in 100 part of solution.
mass % = mass of the component x100 /Total mass of the solution
(2). Volume percentage (V/V) :- volume percentage of a component  

 =   volume of the component x 100 / Total volume of solution 

• Ex-10 % ethanol means 10 mL of ethanol is dissolved in 100 mL water, 
• a 35% ( v/v)Solution of ethylene glycol, an antifreeze, is used in cars for c oohing the engine that lowers the freezing point of water to 255.4K K (17.6℃)

(3). Mass by volume percentage(w/v):-measures the mass of weight of solute in grams vs. the volume of solutions in ml.
(4). Mole fraction (x) :
       mole fraction of a component = no. of moles of the components / total no. of moles of all the components      

                 X_A = n_A  / n_A+ n_B         X_B =     n_B  / n_A+ n_B
we know that  X_A+ X_B= 1
(5)molarity(M):- defined as the number of moles of solute dissolved in one litre (or one cubic diameter) of solution. molarity (M) = moles of solute/Volume of solution in litre
(6). Molality(m):- defined as the no of moles of solute dissolved in one Kg solvent.
                              =moles of solute / mass of solvent in Kg  
Note:-Molarity depends on temperature but molality does not. since molarity depends on volume which varies by temperature.
Solubility of a solid in a liquid : - Every solid does not dissolved in a given liquid. 

• It is observed that polar solutes dissolve in polar solvents & non polar solutes in won polar solvents. ex- NaCl and sugar 
• In general, a solute dissolves in solvent if the intermolecular interactions are similar in the two substances as solute & solvents or we may say like dissolve like .
• solubility depends on - the physical & chemical properties of the solute & solvent as well as on temperature  & presence of other chemicals.
• Effect of temperature on the solubility of solid in a liquid  is significantly affected. It must follow Le Chateliors principle. In general, the dissolution process is endothermic , the solubility should increase with rise in temperature & It is exothermic the solubility should decrease
• pressure does not have any significant effect on solubility of solid in. liquids. it is so because solid & liquids are highly incompressible & practically remain unaffected by changes in pressure.

Dissolution-is the dissolving process of the solid solute while crystallisation is the opposite ,causing the solid solute to remain undissolved.

Saturated solution	Unsaturated solution	Supersaturated solution
Can not dissolve any more quantity of solute in a given amount of solvent at given temperature	Can dissolve more quantity of solute at given temperature	Contains more of the dissolved solute than could be dissolved by solvent under normal circumstances

Solubility of a gas in a liquid: -Many gases dissolve in water . Oxygen dissolves only to a small extent in water. The dissolved oxygen sustain all aquatic life.
The solubility of gases in liquid depends upon-
a). nature of gas & liquid
b).Temperature: solubility of gas in liquid decreases with increase of  temperature. Since K. E. of gas is proportional to temperature. so its escaping tendency will increase with increase of temperature
c). pressure : solubility of gas in liquid increases with increase of pressure. It is so because gas and liquid are compressible.
Henry's law: - Henry was the first to give a quantitatively relation relation between pressure & solubility of a gas in a solvent which is known as Henry's law.
     It states that the solubility of a gas in a liquid is directly proportional to the  partial pressure of the gas present above the surface of liquid or solution at a constant temperature.
           Dalton , a contemporary of Henry , also concluded independently that the solubility of gas in a liquid solution is a function of partial pressure of the gas.
        The most Commonly used form of Henry's law states that " The partial pressure of the gas in vapour phase(p) is proportional to the mole fraction of the gas(x) in the solution". is expressed as:
              p_gas α  x                                      ………..  (1)
              p_gas =K_H x                     ………..  (2)

              here K_H = the Henry’s constant

                      p_gas = partial pressure of the gas

                       x = Mole fraction of the gas

note: solubility of gas decreases with increase of Henry's constant K_H at given pressure .

Applications of Henry's law in industry & some biological phenomena : -

• To increase solubility of CO₂   in soft drinks, beverage, soda water etc.  by applying high pressure and bottles are sealed under high pressure .
• To avoid bends , the tank used scuba divers are filled with air diluted with helium (11.7%helium,56.2 % nitrogen & 32.1 % oxygen) .
• At high altitudes , the partial pressure of oxygen is less . This leads to low concentrations of oxygen in the blood & tissues of people living at high attitudes or climbers. low blood oxygen causes climbers to become weak & unable to think clearly , symptoms of condition known as anoxia.

limitation of Henry's law :- Henry's law is applicable only if the fallowing condition are satisfied -

• • The pressure should be low & temperature should be high i.e. gas should behave a Ideal gas .
  • The gas should not undergo compound formation with solvent or association of dissociation in the solvent .

Next - Vapour pressure of liquid solution, ideal and non-solutions

Next- Azeotropes (constant boiling mixture)- and types

Next-Elevation of boiling point (Ebullioscopy)

Next-Depression of freezing point (cryoscopy)

Next- Osmosis and osmotic pressure

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