Question

i dont know how to balance an equation especially this one !! can someone help asap please

Answer 1

A precipitate forms when a colourless solution of lead nitrate (Pb(NO ) ) is added to a colourless 32
solution of potassium iodide (KI) (Figure 12.2). A dense yellow colour appears that is solid lead iodide. Write a balanced chemical equation, identifying the precipitate.

Answer 2

This is a double replacement reaction: first we figure out what the product will be, and since all nitrates and all potassium compounds are soluble, we can assume that the positive ions will change partners. Balancing merely the CHARGES we get:

Pb(NO3)2 + KI yeilds K(NO3) + PbI2

You see the left has 2 NO3's and the right has only one NO3? This cannot happen, so, we balance the amount of each element and ion by changing the COEFFICIENTS ONLY as such:

Pb(NO3)2 + 2KI yeilds 2K(NO3) + PbI2

PbI2 is not soluble. Halide containing Pb2+ ion. Therefore, this must form a precipiate and the Precipicate is Lead Iodide (PbI2).