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प्रश्न
How do the following help in bringing about a chemical change?
catalyst .
उत्तर
A catalyst can either increases or decreases the rate of chemical reaction and some chemical reactions need a catalyst to change the rate of the reaction, in case it is too slow or too fast
1. Positive catalyst: When a catalyst increase the rate of reaction finely divided iron is used as a positive catalyst in the manufacturing of ammonia from hydrogen and nitrogen.
\[\ce{N2 + 3H2 ⇌[Iron (Catalyst) 200-900][450°C] 2NH3 + Heat}\]
2. Negative Catalyst: When a catalyst decreases the rate of reaction.
Ex. Phosphoric acid act as a negative catalyst to decrease the rate of the decomposition of hydrogen peroxide.
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संबंधित प्रश्न
Classify the following reaction as combination, decomposition, displacement, precipitation and neutralization. Also balance the equation.
\[\ce{NH3_{(g)} + HCl_{(g)} -> NH4Cl_{(s)}}\]
Define precipitation.
How is precipitate formation in a chemical reaction indicated?
Differentiate between in Chemical reaction and chemical equation.
Write balanced chemical equations for the reactions represented by word equations in the conditions for chemical reaction.
What is the reaction called when oxidation and reduction take place simultaneously? Explain with one example.
Explain by writing a word equation.
Bubbles are seen on adding lemon juice to baking soda.
Show with the help of diagram of electronic configuration how the following compound is formed from the constituent atoms.
Potassium fluoride
Give an example of the following chemical change.
Two solids combine to form a liquid
When hydrogen burns in oxygen, water is formed; when electricity is passed through water, hydrogen and oxygen are given out. Name the type of chemical change involved in the two cases.
What do you observe? When
Sodium chloride solution is added to silver nitrate solution.
Complete and balance the following reaction:
\[\ce{Pb(NO3)2 ->[\Delta]}\]
What do you observe when HCI is passed through a silver nitrate solution.
Write your observation and a balanced equation in the case of the following substances being heated.
Zinc carbonate.
Select the correct answer for the following options:
The pale blue precipitated obtained when copper [II] sulphate reacts with sodium hydroxide.
Give reason for the following:
Even though rusting is an exothermic reaction, the heat evolved when an iron nail rusts is unnoticeable.
What is a chemical reaction?
A chemical reaction is often accompanied by external indications or characteristics which include –
- Colour change
- Effervescence or gas evolved
- Evolution or absorption of heat
- Formation of a precipitate.
With reference to each of the above indications, state the external indication seen during – Addition of dilute hydrochloric acid to silver nitrate.
A chemical reaction is often accompanied by external indications or characteristics which include –
- Colour change
- Effervescence or gas evolved
- Evolution or absorption of heat
- Formation of a precipitate.
With reference to each of the above indications, state the external indication seen during – Addition of water to quicklime.
Complete the table given below.
| Addition of dil. H2SO4 to KHCO3 | Name of residue obtained |
State the following reaction represent oxidation or reduction.
\[\ce{Ag->Ag+}\]
Name the solid residual product formed reaction and state its colour during – thermal decomposition of the following substance.
Ammonium dichromate.
Higher order Thinking question
Peeled and unpeeled banana does not look the same. Does that mean peeling banana is a chemical change?
Chemists identify gypsum as a natural indicator.
Give two examples for each of the following cases:
Chemical changes.
If you leave a piece of iron in the open for a few days, it acquires a film of brownish substance, called rust.
Can you change rust back into iron by some simple method?
Galvanization is a process in which ______ is coated as a layer of iron.
Which is used as a catalyst during the process of hydrogenation of oils?
Chemical changes are important in our day-to-day life. Give examples.
Acid rain is a result of ______.
