Advertisements
Advertisements
प्रश्न
How do the following help in bringing about a chemical change?
catalyst .
Advertisements
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.
APPEARS IN
संबंधित प्रश्न
How do the following help in bringing about a chemical change?
pressure.
TRUE \ FALSE
Ammonia is a good oxidizing agent.
Write a short note on the information derived from a balanced chemical equation.
Copper carbonate when heated, it turns :
What is the reaction called when oxidation and reduction take place simultaneously? Explain with one example.
Explain by writing a word equation.
Limestone powder disappears on adding to dilute hydrochloric acids.
Explain by writing a word equation.
Bubbles are seen on adding lemon juice to baking soda.
What is a chemical change? Give two examples of chemical change?
Give an example of a photochemical reaction.
Select the correct answer for the following options:
The black residue obtained on heating copper carbonate.
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.
Give balanced equation for the following conversion affected by heat alone on the substance:
Zinc carbonate to zinc oxide
The chemical change is ______.
Chemical change is a temporary change.
Silver articles turning black: ______:: Boiling of H2O: physical change ______.
Two chemical species X and Y combine together to form a product P which contains both X and Y
\[\ce{X + Y -> P}\]
X and Y cannot be broken down into simpler substances by simple chemical reactions. Which of the following concerning the species X, Y and P are correct?
(i) P is a compound
(ii) X and Y are compounds
(iii) X and Y are elements
(iv) P has a fixed composition
Write a note on the following:
Curdling of milk
When carbon dioxide is passed through lime water ______.
Define the following term:
Chemical change
