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
When baking soda is mixed with lemon juice, bubbles are formed with the evolution of a gas. What type of change is it? Explain.
How do the following help in bringing about a chemical change?
heat.
MULTIPLE CHOICE QUESTIONS
Tick the most appropriate answer.
Reduction reaction is the exact opposite of
- displacement reaction
- decomposition reaction
- oxidation reaction
- none of these
Differentiate between in Chemical reaction and chemical equation.
Explain by writing a word equation.
Bubbles are seen on adding lemon juice to baking soda.
Explain,giving one example of the following chemical changes:
Reversible reaction
What do you understand by 'chemical reaction'?
Give an example of the following chemical changes.
A reaction where colour change is noticed.
Complete and balance the following reaction:
\[\ce{Pb(NO3)2 ->[\Delta]}\]
What do you observe when HCI is passed through a silver nitrate solution.
Give a chemical test to distinguish between the following gases.
HCl and Cl2
On heating which of the following substances i.e. copper carbonate, zinc carbonate, washing soda, copper sulphate, zinc nitrate, copper nitrate, lead nitrate, ammonium chloride and ammonium dichromate – relate to the reaction given below.
A white solid which evolves two colourless gases which on cooling combine and condense on the cooler parts of the test tube.
Give balanced equation for the following conversion affected by heat alone on the substance:
Zinc nitrate to nitrogen dioxide
Higher order Thinking question
A very hot glass on putting in cold water cracks. What does this change indicate?
Discuss how acid rain occurs due to emission of smoke from vehicles and industries?
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
We are advised to not to play with fireworks. Give reason.
Assertion (A): Cutting paper into very small pieces is an irreversible change.
Reason (R): Physical changes are always reversible.
______ is the chemical name of limestone.
