<span>Clouds are made of tiny drops of water or ice crystals that settle on dust particles in the atmosphere. The droplets are so small - a diameter of about a hundredth of a millimetre - that each cubic metre of air will contain 100 million<span>droplets</span></span>
Balanced chemical reaction:
2Na₃PO₄(aq) + 3CaCl₂(aq) → 6NaCl(aq) + Ca₃(PO₄)₂(s).
Ionic reaction:
6Na⁺(aq) + 2PO₄³⁻(aq) + 3Ca²⁺(aq) + 6Cl⁻(aq) → 6Na⁺(aq) + 6Cl⁻(aq) + Ca₃(PO₄)₂(s).
Net ionic reaction: 2PO₄³⁻(aq) + 3Ca²⁺(aq) → Ca₃(PO₄)₂(s).
<span>(aq) means that
substances are dissociated on cations and anions in water.
</span>(s) means solid.
Answer: A) 3.21 g
Explanation:
According to the law of conservation of mass, mass can neither be created nor be destroyed. Thus the mass of products has to be equal to the mass of reactants. The number of atoms of each element has to be same on reactant and product side.

We are given:
Mass of iron = 5.58 g
Mass of iron sulphide = 8.79 g
Mass of sulphur = x g
Total mass on reactant side = 5.58 + x
Total mass on product side = 8.79 g
Applying law of conservation of mass, we get:
Hence, the mass of reacting sulfur is 3.21 g.
By adding together the number of protons and neutrons and multiplying by 1 amu, you can calculate the mass of the atom.