HW-3 Types of chemical equations. 29 APR 2020

HW-3
Types of chemical equations. 29 APR 2020

1.     What do you understand by the term “Combination reaction”? Write any two examples.

2.     What do you understand by the term “Decomposition reaction”?

3.     What do you understand by the term “Electrolysis”? Write an example.

4.     What do you understand by the term “Thermal decomposition reaction”? Write an example.

5.     What do you understand by the term “Photochemical decomposition reaction”? Write an example.

6.     What do you understand by the term “Displacement reaction”? Write any two examples.

7.     What do you understand by the term “Double displacement reaction”? Write an example.

8.     What do you understand by the term “Precipitation reaction”? Write any two examples.

9.     What do you understand by the term “Neutralization reaction”? Give an example and two uses.

10.                         What do you mean by “REACTIVITY SERIES OF ELEMENTS”?

Note: Please refer NCERT SCIENCE TEXT BOOK OF CLASS.X- Pages 6 to 11.

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Answer Key for HW-3
Types of chemical equations. (29 APR 2020)

1.     What do you understand by the term “Combination reaction”? Write any two examples.

Answer: COMBINATION REACTION • In combination reaction, two or more substances combine to form a new substance • For example
• C(s) + O₂ (g)           CO₂ (g)
• 2H₂ (g) + O₂ (g)            2H₂O (g)

2.     What do you understand by the term “Decomposition reaction”? Write any two examples.

Answer: DECOMPOSITION REACTION • In a decomposition reaction, a single compound breaks down to produce two or more similar substances. • The decomposition reactions take place when energy is supplied in the form of heat, electricity or light.

3.     What do you understand by the term “Electrolysis”? Write any two examples.

Answer: ELECTROLYSIS • When a substance is decomposed by passing electric current, the process is called electrolysis.
 2H₂O (I)        electricity             2H₂ (g) + O₂ (g)

4.     What do you understand by the term “Thermal decomposition reaction”? Write an example.

Answer: THERMAL DECOMPOSITION • When a substance decomposes on heating it is called thermal decomposition.
 CaCO₃ (S)       heat           CaO (S) + CO2 (g)

5.     What do you understand by the term “Photochemical decomposition reaction”? Write an example.

Answer: PHOTOCHEMICAL DECOMPOSITION • When a substance is decomposed in presence of sunlight, it is called a photochemical decomposition.
 AgBr     sunlght                Ag +Br

6.     What do you understand by the term “Displacement reaction”? Write any two examples.

Answer: DISPLACEMENT REACTION • In a displacement reaction, a more reactive metal displaces or removes another element from a compound.

• For example • Zn(s) + CuSO4 (aq)                ZnSO4(s) +Cu In the above reaction Zn is more reactive Cu, so Zn displaces Cu from CuSO4.
• 2AgNO₃ (aq) + Zn(s) → 2Ag(s) + Zn(NO3)2 (aq) In the above reaction Zn is more reactive than Ag , so Zn displaces Ag from its solution.

7.     What do you understand by the term “Double displacement reaction”? Write any two examples.

Answer: DOUBLE DISPLACEMENT REACTION • The reaction in which two different atoms or group of atoms are displaced by other atoms or groups of atoms are double displacement reaction. • For example • BaCl₂ (aq) + Na₂SO_{4 (}aq)             BaSO₄(s) + 2NaCl (aq)

8.     What do you understand by the term “Precipitation reaction”? Write any two examples.

Answer: PRECIPITATION REACTION • Precipitation reactions occur when cations and anions in aqueous solution combine to form an insoluble ionic solid called a precipitate.
 AgNO3 + NaCl             AgCl + NaNO3

9.     What do you understand by the term “Neutralization reaction”? Give an example and two uses.

Answer: NEUTRALIZATION REACTION • A neutralization is a type of double replacement reaction. • In the reaction, H+ and OH- combine to form HOH or H2O or water molecules. • A salt is the product of an acid-base reaction. • For example
 HCl + NaOH               NaCl +H₂O

Uses:          As an antacid (a base which gives relief from acidity in stomach).
      As tooth paste which prevent tooth decay.

10.                        What do you mean by “REACTIVITY SERIES OF ELEMENTS”?

Answer: REACTIVITY SERIES OF METALS • Reactivity series of metals is a series in which the elements arranged in the decreasing order of their reactivity.

Please Note: Each question carries one mark. If all your Answers are correct you will score 10 out of 10, if nine of your Answers are correct you will score 9 out of 10, if eight of your Answers are correct you will score 8 out of 10. Likewise check your HW with today’s date and award marks accordingly.

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