class 10th chapter 1st science (chemical Reaction and Equation) short question.
Answers
the symbolic representation of a chemical reaction is chemical equation
Answer:
Hi
Explanation:
Solution:
An endothermic reaction occurs when energy is absorbed from the surroundings in the form of heat.(Example: Photosynthesis, melting of ice, evaporation). Conversely, an exothermic reaction is one in which energy is released from the system into the surroundings. (Example: Explosions, concrete setting, nuclear fission and fusion).
10. Why is respiration considered to be an exothermic reaction?
Solution:
For the survival of life, we require energy. We obtain this energy from the food we eat. The food molecules, through the process of digestion, is broken down into a simpler molecule like glucose. These substances come in contact with the Oxygen present in our body cells to form Carbon dioxide and water along with a certain amount of energy(Respiration process). Since the energy is in the form of heat(that maintains our body temperature) the respiration is considered to be an exothermic reaction. The reaction taking place is:
C6H12O6+6O2→6CO2+6H2O+Energy
11. Why are decomposition reactions called the opposite of Combination reactions? Write equations for decomposition reactions.
Solution:
Combination reaction is said to be the reaction between two or more molecules to form a larger molecule; whereas the decomposition reaction is defined as the splitting of larger molecules into two or more smaller molecules. This essentially explains that the decomposition reaction is the opposite of the combination reaction.
Solution:
(a) Thermal decomposition reaction (Thermolysis)
Decomposition of potassium chlorate: When heated strongly, potassium chlorate decomposes into potassium chloride and oxygen. This reaction is used for the preparation of oxygen.
2KClO3+Heat→2KCl+3O2
(b) Electrolytic decomposition reaction (Electrolysis)
Decomposition of sodium chloride: On passing electricity through molten sodium chloride, it decomposes into sodium and chlorine.
2NaCl→electricity 2Na+Cl2
(c) Photodecomposition reaction (Photolysis)
Decomposition of hydrogen peroxide: In the presence of light, hydrogen peroxide decomposes into water and oxygen
2H2O2 (light) → 2H2O+O2
13. What is the difference between displacement and double displacement reactions? Write relevant equations for the above.
Solution:
A displacement reaction is the one when a more reactive substance displaces a less reactive one from its salt solution whereas a double displacement reaction is the one where a mutual exchange of ions happens between two compounds.
In a displacement reaction, only a single displacement takes place whereas in the double displacement reaction, as the name suggests two displacement takes place between the molecules.
Example:
Displacement reaction
Mg+2HCl→MgCl2+H2
Double displacement reaction
2KBr+BaI2→2KI+BaBr2
Q14) What is the difference between displacement and double displacement reactions? Write relevant equations for the above.
Solution:
A displacement reaction is the one when a more reactive substance displaces a less reactive one from its salt solution whereas a double displacement reaction is the one where a mutual exchange of ions happens between two compounds.
In a displacement reaction, only a single displacement takes place whereas in the double displacement reaction, as the name suggests two displacement takes place between the molecules.
Example:
Displacement reaction
Mg+2HCl→MgCl2+H2
Double displacement reaction
2KBr+BaI2→2KI+BaBr2
15. In the refining of Silver, the recovery of silver from Silver nitrate solution involves displacement reaction by Copper metal. Write down the reaction involved.
Solution:
Cu(s)+2AgNO3(aq)→Cu(NO3)2(aq)+2Ag(s)
16. What do you mean by a precipitation reaction? Explain by giving examples.
Solution:
When two solutions containing soluble salts are combined, a double displacement reaction takes place in which the ions are exchanged between the compounds. When one of such compounds formed is in solid form (that is insoluble in aqua) then it settles down at the bottom of the container. This solid is known as the precipitate and the respective reaction is termed as the precipitation reaction. Few examples of precipitation reactions are:
CdSO4(aq)+K2S(aq)→CdS(s)+K2SO4(aq)
2NaOH(aq)+MgCl2(aq)→2NaCl(aq)+Mg(OH)2(s)