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प्रश्न
Write true or false :
When iron and sulphur are heated together a grey mass is formed which is attracted by a magnet .
विकल्प
True
False
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उत्तर
False
APPEARS IN
संबंधित प्रश्न
How do the following help in bringing about a chemical change?
catalyst .
Complete and balance the following chemical equations
Na + H2 O →
MULTIPLE CHOICE QUESTIONS
Tick the most appropriate answer
Which of the following is a reducing agent?
- oxygen
- chlorine
- hydrogen
- none of these
MULTIPLE CHOICE QUESTIONS
Tick the most appropriate answer.
Miscible liquids having slightly different boiling points can be separated by the
- evaporation
- distillation
- fractional distillation
- sedimentation
What are chemical reactions?
State what you would observe when the following substance is heated in a glass test tube Copper (II) carbonate Red lead .
Distinguish by heating the following in dry test tubs.
Zinc carbonate, Copper carbonate and lead carbonate.
Select the correct answer for the following options:
The gas which reacts with oxygen to give a neutral liquid.
Give reason for the following:
Even though rusting is an exothermic reaction, the heat evolved when an iron nail rusts is unnoticeable.
Give reason for the following:
The catalytic oxidation of sulphur dioxide to sulphur trioxide is represented by a double arrow {⇌}
between the reactants and products, formed in the 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.
Give balanced equation for the following conversion affected by heat alone on the substance:
Hydrated copper sulphate to sulphur dioxide
Complete the table given below.
| Heat on iodine crystals | Colour of vapours evolved |
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
The simplest method of preventing rusting of iron is to coat it with oil, grease, or paint. The reason being ______.
The chemical formula of rust is ______.
How can we prevent rusting?
______ is the chemical name of rust.
Acid rain is a result of ______.
Define the following term:
Chemical change
