Chemistry
Assertion (A): Chemical combination always takes place between two elements.
Reason (R): A single substance is formed in a chemical combination.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true but R is not the correct explanation of A.
- A is true but R is false.
- A is false but R is true.
Chemical Reaction
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Answer
A is false but R is true.
Explanation — Chemical combination may take place between two or more elements. Hence, the assertion (A) is false.
A compound is a substance formed by the chemical combination of two or more elements in a fixed proportion. So, a single substance is formed in a chemical combination. Hence, the reason (R) is true.
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Related Questions
Assertion (A): Magnesium phosphate is written as Mg3(PO4)2.
Reason (R): The valencies of magnesium and phosphate are three and two respectively.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true but R is not the correct explanation of A.
- A is true but R is false.
- A is false but R is true.
Assertion (A): A chemical equation is written to represent molecules.
Reason (R): This is necessary for the law of conservation of mass
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true but R is not the correct explanation of A.
- A is true but R is false.
- A is false but R is true.
Fill in the blanks:
(a) Dalton used symbol …………… for oxygen and …………… for hydrogen.
(b) Symbol represents …………… atom of an element.
(c) Symbolic expression for a molecule is called …………… .
(d) Sodium chloride has two radicals. Sodium is a …………… radical while chloride is a …………… radical.
(e) Valency of phosphorus in PCl3 is …………… and in PCl5 is …………… .
(f) Valency of Iron in FeCl2 is …………… and in FeCl3 it is …………… .
(g) Formula of iron (III) carbonate is …………… .
Complete the following table.
Acid Radicals →
Basic Radicals ↓Chloride Nitrate Sulphate Carbonate Hydroxide Phosphate Magnesium MgCl2 Mg(NO3)2 MgSO4 MgCO3 Mg(OH)2 Mg3(PO4)2 Sodium Zinc Silver Ammonium Calcium Iron (II) Potassium