Class 10 Science Important Questions in Chemical Reactions and Equations

Are you studying 10 classes? students need science class 10 important questions and chemical reactions equations.

1. (a) Define the equilibrium chemical equation. Why balance the equation?

(B) Write the equilibrium chemical equation for the following reaction:
(i) Phosphorus is burned in the presence of chlorine to form pentachloride.
(ii) Combustion of natural gas.
(iii) Respiratory process.

The answer.

A. An equilibrium chemical equation consists of an equal number of atoms of different elements in reactions and products. According to the Mass Conservation Act, matter cannot be created or destroyed in a chemical reaction.

Chemical reaction.
B. i) P4(s) + 10Cl2 (g) ———> 4PCl5 (S)
(ii)CH4 (g) + 2O2 (g) ———> CO2 (g) + 2H2O(l) + heat energy
(iii) C6H12O6 (s) + 6O2 (g) + 6H2O ———> 6CO2 (aq) + 12H2O (l) +energy

2.(a) Explain two ways by which food industries prevent rancidity.

(b) Discuss some essential decomposition reactions in the metal industry with three points.
Answer.
(A)(i) Rancidity can be prevented by including antioxidants in the diet
Fat and oil, e.g. Butylated hydroxy anisole is added to butter as an antioxidant.
(ii) This can be prevented by packaging foods containing fat and oil containing nitrogen gas.
(B) (i) Dissolved NaCl sodium decomposes electrolyte to form metal.
(ii) Aluminum metal can be obtained by electrical decomposition of bauxite ore mixed with cryolite.

3. An example list is two pieces of information that make the chemical equation more useful (informative).

The answer.
(i) The physical state of the reactions must be specified, e.g.
2H2 (g) + O2 (g) —–– 2H20 (l)
(ii) The reaction situation is written on the arrow head, e.g.

Consider the following chemical reaction
X + barium chloride +Y + sodium chloride
(White PPT)
(A) Identify ‘X’ and ‘Y’
(B) Type of reaction
(A) ‘X’ Na2SO4 and Y baso4.
(b) The type of reaction
Na2SO4 + BaCl2—–> BaSO4 + 2NaCl
(White ppt)
The reaction is precipitation reaction. It is also called double displacement reaction.

4. We need to balance the skeletal chemical equation. ”Give reason to justify the statement.

Answer: Skeletal chemical equations are unbalanced. We have to balance the chemical equations because of the mass conservation law. ‘Material cannot be created, cannot be destroyed’. Therefore the chemical equations must have a balance in everything

5. Write the chemical equation of the reaction with the following changes with each example

(i) Change in color
(ii) Change in temperature
(iii) Precipitation formation

Answer.
(i) Cu (s) + 2AgNO3 (aq)> -> Cu (NO3) 2 (aq) + 2Ag
The solution turns blue and a shiny silver metal is deposited.
(ii) NaOH + HCl> -> NaCl + H2O + heat
As the temperature rises the heat evolves.
(iii) Pb (NO3) 2 (aq) + 2KI (aq)> -> Pbl2 (s) + 2KNO3 (aq) Yellow ppt

6.(A) Describe two ways in which the food industry can prevent rancidity

(B) Discuss the importance of the decomposition reaction in the metal industry with three points.

Answer.
(i) Rancidity can be prevented by including antioxidants in the diet Fat and oil, e.g. Butylated hydroxy anisole is added to butter as an antioxidant.
(ii) This can be prevented by packaging foods containing fat and oil containing nitrogen gas.

(i) Dissolved NaCl sodium decomposes electrolyte to form metal.
(ii) Aluminum metal can be obtained by electrical decomposition of bauxite ore mixed with cryolite.
(iii) Thermally when Carbonate ores are decomposed gives metal oxide which on reduction gives metal.

7. What is a skeletal type chemical equation? What does this mean? Using the equation for water electrolysis decomposition, distinguish between the skeletal chemical equation and the equilibrium chemical equation.

The answer. Gas written equations and equations in the form of molecules instead of atomic form are not in equilibrium, which is called the skeletal type equation. They represent the gaseous elements formed in the atomic state and
H2o=H+o (Skeletal equation)
Hydrogen and oxygen are written in atomic forms and equation is not balanced
H2o=H2+O2 is also skeletal equation
2H2= 2H2+O2 (Balanced Chemical equation)

8. What is the color of ferrous sulfate crystals?How does this color change after heating?

Answer. The color of the ferrous sulphate is light green.due to the formation of iron oxide the color changes to reddish brown on heating.Give each example of thermal decomposition and photochemical decomposition reactions. Also write the relevant equilibrium chemical equations.Thermal decomposition reaction:

CuCO3(s) =CuO9(s)+ CO2(g)

9. Write any two observed activities that indicate that a chemical reaction has taken place. Give an example in support of your answer.

The answer. These two observations indicate that any chemical reaction has taken place.
(i) Change in status.
(ii) Change in color.
(iii) Evolution of gas.
(iv) change in temperature.

For example, lead nitrate is a white crystalline solid that gives a yellowish brown solid (lead monoxide) upon heating. Brown gas and colorless gas also emerged.

10. What do you mean by exothermic and endothermic reactions? Give examples.

Answer. Exothermic reactions are those in which heat is evolved, e.g.
What do you mean by exothermic
Endothermic reactions are those reactions in which heat is absorbed, e.g.
What do you mean by endothermic reactions

Conclusion:

Chemical Reactions and Equations 5 mark Important Questions .Keep studying all questions and answer. Keep practicing equations. It helps you in 11th classes. For more questions read textbooks.

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