Answer
(1) $Pb^{2+}_{(aq.)}$ is present because the yellow $PbCrO_4$$_{(s)}$ is formed.
(2) $Hg_2^{2+}$$_{(aq.)}$ is absent because the observation of the test for that ion negative.
(3) $Pb^{2+}_{(aq.)}$ presence is not confirmed because it
really was not tested for.
Work Step by Step
(1) $Pb^{2+}_{(aq.)}$ is present because the yellow $PbCrO_4$$_{(s)}$ is formed.
(2) $Hg_2^{2+}$$_{(aq.)}$ is absent because the observation of the test for that ion negative.
(3) $Pb^{2+}_{(aq.)}$ presence is not confirmed because it
really was not tested for.
