Q1
The law of conservation of mass states that in a chemical reaction, mass is:
📝 SolutionThe law of conservation of mass says that mass can neither be created nor destroyed in a chemical reaction. The total mass of reactants equals the total mass of products.
Q2
Who gave the atomic theory that matter is made of tiny indivisible particles called atoms?
📝 SolutionJohn Dalton proposed the atomic theory, stating that matter is made of small indivisible particles called atoms with definite mass.
Q3
The chemical symbol for sodium is:
📝 SolutionThe symbol for sodium is Na, taken from its Latin name 'Natrium'. Symbols often come from Latin names for older-known elements.
Q4
What is the molecular mass of water ($H_2O$)? (H = 1, O = 16)
📝 SolutionMolecular mass of $H_2O$ = 2(1) + 16 = 18 u. Add the atomic masses of two hydrogen atoms and one oxygen atom.
Q5
One mole of any substance contains how many particles (Avogadro's number)?
📝 SolutionOne mole contains Avogadro's number of particles, $6.022 \times 10^{23}$, whether atoms, molecules or ions.
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Class 9 · Science
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