sat chem 2 questions. need help

<p>Na2CrO4, a soluble yellow solid
PbCrO4, an insoluble yellow solid
NaNo3, a soluble white solid
Pb(NO3)2, a soluble white solid</p>

<p>(A) yellow solid and colorless solution
(B) yellow solid and yellow solution
(C) white solid and colorless solution
(D) no solid and yellow solution
(E) no solid and colorless solution</p>

<p>im not quite sure how to do these problems =/</p>

<h1>5 Observed when 3.0 mol of Na2CrO4 and 1.0 mol of Pb(NO3)2 are mixed with 1 L of water.</h1>

<h1>113 A 1 mol sample of electrons is required to reduce 0.5 mol of chlorine gas to chloride ions</h1>

<p>BECAUSE
chlorine molecules are diatomic and the charge on the chloride ion is -1</p>

<p>okay i get the second part, but not the first. can someone show the work for that part</p>

<p>and i was just wondering if there's any organic chem on the test, cause i really don't feel like reviewing that stuff. </p>

<p>thanks</p>

<p>I need help on these problems too, anyone? are we supposed to know the colors of precipitates?</p>

<p>Number five is a double replacement reaction. The products are lead chromate and sodium nitrate. Thus, you have a yellow solid(lead chromate) and a colorless solution(sodium nitrate). If you did this in lab the solution would appear yellow, but that is with the precipitate present in the beaker. The actual solution is colorless. Answer-A</p>

<p>For the first part of that CE question, write out the reduction reaction. </p>

<p>2e- + Cl2 –> 2Cl^-1 </p>

<p>The question asks if 1 mole of electrons is needed to reduce .5 moles of dichlorine gas. This is true because 2 moles of electrons are needed to reduce 1 mole of diatomic chlorine; thus, the ratios are the same. I am not necessarily sure if it is CE though, but I would fill it in because it is because of the diatomic gas and charges that cause the mole-to-mole ratios to be the way they are.</p>