Sample Questions from ADA DAT test

[vDDmaniaC]

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51. DUring a titration it was determined that 30ml of a 0.1M Ce^4+ solution was required to react completely with 20ml of a 0.15M Fe^2+ solution. How do I find the reaction equation? All I know is MV is the same for both of cases, 3. Does that affect the number of ions for each atom?

66. How many lewis structures for NO3^- are there? THe total number of ground state resonance structure for this ion ? I know what we have to do first. That is to find the total valence electrons which are 5+6x3+1=24
Then try to fit in octet rule... but next step is kinda lost. Sometimes N can bond to O with double bond and somtimes not so as holding proton or electron. I don't know why specifically.

A.1 B.2 C.3 D.4 E.5

Plz, help!

 

[chessxwizard]

51. The trick to this question is the word "completely". This tells us that both reactants were consumed completely, at a particular ratio given by the equation of the reaction. Figure out how many moles of each substance are reacting to find the ratio of the ions by multiplying volume by molarity. Since it's a 1:1 ratio, pick the reaction in the answer choices that has the same thing.

66. There are three lewis structures that satisfy the NO3- ion, basically the same thing as the picture but with the double bond between the nitrogen and the left and the right oxygen ion. The resonance hybrid is about 33% of each of those structures. Not sure what you are saying about holding a hydrogen or not; the question specifically asks for the ion, not HNO3. You're on the right track with finding the electrons: there are 12 pairs. Connect the N with the O, you're left with 9. 3 electron pairs around every oxygen, leaving 2+ charge on N with 3 bonding pairs and -1 on each oxygen atom with 3 valence pairs each. Double bond between O and N to give N the octet, and you're finished.