Advertisements
Advertisements
प्रश्न
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 – Thermal decomposition of mercury [II] oxide.
उत्तर
Thermal decomposition of mercury [II] oxides: Red colour of Hg[II]0 changes to silvery (Hg metal).
APPEARS IN
संबंधित प्रश्न
What are (i) positive catalysts and (ii) negative catalysts? Support your answer with one example for each of them.
Complete and balance the following chemical equations:
\[\ce{Pb(NO3)2->[heat]}\] _________
Fill in the blanK
A .............is a substance which changes the rate of a chemical reaction without undergoing a chemical change.
TRUE \ FALSE
Copper can displace iron from iron sulphate.
TRUE \ FALSE
Weak electrolytes dissociate partially in their aqueous or fused state.
Fill in the blank.
Melting of ice is a _______ change.
Copper carbonate when heated, it turns :
Write balanced chemical equations for the reactions represented by word equations in the conditions for chemical reaction.
Give reason for the following:
Blue solution of copper sulphate changes to green when a piece of iron is added to this solution.
What do you understand by precipitation reaction? Explain with examples.
What is a chemical change? Give two examples of chemical change?
Define:
Photochemical reaction
Give one example
Complete and balance the following reaction:
\[\ce{NH3 + O2 ->[\Delta]}\]
Name: Two carbonates do not produce carbon dioxide on heating.
Give a chemical test to distinguish between the following gases.
H2 and CO2
What do you observe when CO2 is passed through lime water first and then a little in excess.
Explain the term ‘chemical reaction’ with special reference to – ‘reactants’ and ‘products’.
Give reason for the following:
A characteristic change of colour is seen when a piece of iron is added to copper [II] sulphate solution.
State the following reaction represent oxidation or reduction.
\[\ce{Cu++->Cu}\]
Explain the term chemical reaction with special reference to reactants and products.
Give a balanced equation for the conversion of a soluble lead salt to an insoluble lead salt – formed as a white precipitate.
Differentiate between the following:
Neutralization reaction and a precipitation reaction.
Higher order Thinking question
Peeled and unpeeled banana does not look the same. Does that mean peeling banana is a chemical change?
Higher order Thinking question
A very hot glass on putting in cold water cracks. What does this change indicate?
______ occurs in the absence of air and in the presence of micro-organisms such as yeast.
The chemical formula of rust is ______.
Is the conversion of milk into ice cream a chemical change?
Assertion (A): Cutting paper into very small pieces is an irreversible change.
Reason (R): Physical changes are always reversible.
Define the following term:
Chemical change
