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सी.आई.एस.सी.ई.आयसीएसई ICSE Class 8

Define Catalyst. - Chemistry

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प्रश्न

Define catalyst.

व्याख्या
एका वाक्यात उत्तर

उत्तर

A catalyst is a substance that either increases or decreases the rate of a chemical reaction without itself undergoing any chemical change.
\[\ce{N2 + 3H2 ⇌[Iron (Catalyst) 200 - 900][450°C] 2NH3 + Heat}\]
here iron act as a catalyst and increases the rate of chemical reaction.

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पाठ 6: Chemical Reactions - Exercise 2 [पृष्ठ ८६]

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सेलिना Concise Chemistry [English] Class 8 ICSE
पाठ 6 Chemical Reactions
Exercise 2 | Q 3.3 | पृष्ठ ८६

संबंधित प्रश्‍न

Complete and balance the following chemical equations:

Fe `"SO"_4`  + NaOH  `→`

   (aq.)          (aq.)


Complete and balance the following chemical equations:

\[\ce{Pb(NO3)2->[heat]}\] _________


MULTIPLE CHOICE QUESTIONS

Tick the most appropriate answer.

Reduction reaction is the exact opposite of

  1. displacement reaction
  2. decomposition reaction
  3. oxidation reaction
  4. none of these

What are homogenous reactions ?


 Fill in the blank

A new substance is formed in a _______ change.


Define the following terms

Precipitate


Write the chemical reaction where the following changes are observed.

Colour change is noticed


Give reason for the following:

Colourless concentrated sulphuric acid in a test tube changes to blue on adding a small piece of copper to it.


Complete and balance the following reaction:

Pb(NO3)2 + KI →


State the original colour of the following substance and colour of residue obtained after heating.

Ammonium dichromate


State the original colour of the following substance and colour of residue obtained after heating.

Lead nitrate


Write your observation and a balanced equation in the case of the following substances being heated.

Copper nitrate. 


A chemical reaction is often accompanied by external indications or characteristics which include – 

  1. Colour change
  2. Effervescence or gas evolved
  3. Evolution or absorption of heat
  4. Formation of a precipitate.

With reference to each of the above indications, state the external indication seen during – Addition of dilute acid to an active metal.


Give balanced equation for the following conversion affected by heat alone on the substance:

Copper carbonate to copper oxide


Complete the table given below.

Heat on  copper carbonate Test for gas evolved  

State the following reaction represent oxidation or reduction.

\[\ce{Cl- ->Cl}\]


Give a balanced equation for a reaction involving the evolution of gas on the addition of dilute acid to sodium sulphite.


Name the solid residual product formed reaction and state its colour during – thermal decomposition of the following substance.

Copper nitrate.


Circle the odd one out. Give reason for your choice


______ gas causes tears in our eyes while cutting onions.


Discuss how acid rain occurs due to emission of smoke from vehicles and industries?


Which of the following is not an “element + element → compound” type reaction?


Can a nickel spatula be used to stir copper sulphate solution? Justify your answer.


Classify the following as physical or chemical properties

Zinc dissolves in hydrochloric acid with the evolution of hydrogen gas.


A chemical change may involve –


Vanaspati is obtained from vegetable oils by the addition of ______ to the oils.


The simplest method of preventing rusting of iron is to coat it with oil, grease, or paint. The reason being ______.


______ is a chemical substance is used in whitewashing.


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