When a solution of ammonium sulfate is added to a solution of strontium nitrate, Sr(NO3)2, a white precipitate, strontium sulfate, forms. Write a balanced net ionic equation for this reaction. Both ammonium sulfate and strontium nitrate, Sr(NO3)2 exist as
dissociated ions in aqueous solution.

SO₄²⁻(aq) + Sr²⁺(aq)      →    SrSO₄(s)

Explanation:

Chemical equation:

(NH₄)₂SO₄(aq) + Sr(NO₃)₂(aq)    →    NH₄NO₃(aq) + SrSO₄(s)

Balance chemical equation:

(NH₄)₂SO₄(aq) + Sr(NO₃)₂(aq)    →    2NH₄NO₃(aq) + SrSO₄(s)

Ionic equation:

2NH₄⁺(aq)  + SO₄²⁻(aq) + Sr²⁺(aq)  +2NO₃⁻(aq)    →    2NH₄⁺(aq)  + 2NO₃⁻(aq) + SrSO₄(s)

Net ionic equation:

SO₄²⁻(aq) + Sr²⁺(aq)      →    SrSO₄(s)

The NH₄⁺(aq) and NO₃⁻(aq)  are spectator ions that's why these are not written in net ionic equation. The strontium sulfate can not be splitted into ions because it is present in solid form.

Spectator ions:

These ions are same in both side of chemical reaction. These ions are cancel out. Their presence can not effect the equilibrium of reaction that's why these ions are omitted in net ionic equation.  

heat or electricity in the atmosphere- c.

vanderwaal's forces of attraction are the electrostatic intermolecular forces that exist in a molecule due to the temporary or permanent dipoles that are developed in a molecule. in , the major intermolecular forces are dipole-dipole interactions as the molecule is polar (bent structure). so the vanderwaal's forces of interaction in between molecules are the permanent dipole-dipole interactions that develop due to the dipole that exists in between the polar h - s bond. the positively charged hydrogen atom is attracted towards the negative end of the dipole that is sulfur of the adjacent molecule. therefore, these forces of attraction are relatively stronger than that of london dispersion forces that exist in non polar molecules.