The answer should be 2KI(aq)+Hg(NO3)2(aq) = 2KNO3(aq) + HgI2(s). This is a double replacement reaction, the valence of elements will not change. The HgI2 is not soluble in water.
They do this in order to survive their new environment. If they didn't adapt, then they would die!
It would be considered a Homogeneous Mixture. A mixture with two or more components mixed evenly is a Homogeneous mixture.
