SAT2 Chem ?'s

Test Preparation SAT Subject Test Preparation
1

<p>How can you tell if a compound is ionic or covalent without knowing electronegativities (im assuming the sat2 test doesnt provide electronegativities)</p>

<p>theres this question in the barron's sat 2 book that asks</p>

<p>all of the following have covalent bonds except</p>

<p>HCL
som eother choices...
CsF</p>

<p>i put Hcl which was wrong, because it's polar covalent from electronegativity difference, although its a metal + a nonmetal, which is usually ionic. answer was CsF.</p>

2

<p>and here’s another question for u guys</p>

<p>list molecular forces from weakest to strongest</p>

<p>just a few to list (in no particular order)
dipole-dipole
coordinate covalent
covalent
polar covalent
ionic
london dispersion forces
van der waals</p>

3

<p>yet another help request…</p>

<p>what are sigma and pi bonds, i completely dont understand them at all, i dont think i ever learned about them in honors chem.</p>

<p>it has to do with sp2, sp3, orbitals and molecular shape, which im not very good at…</p>

<p>help appreciated</p>

4

<p>@qwerfsad:
basically, the electronegativities increase across a period
and increase going up a group</p>

<p>so…basically, it’s a diagonal increase.
therefore, Cs and F, which are really far apart on the table, are ionically bonded.</p>

5

<ol>
<li>Treat Hydrogen as nonmetal generally. It almost never forms ionic bonds. Cesium is a metal, and Florine is a non-metal. This pairing results in ionic bonding, i.e. not covalent.

I wouldn’t call it a diagonal increase. Just remember the first two parts. The implication of calling it a diagonal increase is that Oxygen and Chlorine have equal electro negativities. However, Oxygen is significantly more electronegative. So don’t think of it in that way.</p>

6

<p>which has higher electronegativity, Br or Kr</p>

<p>Br is a halogen with a 1- ion while Kr is a noble gas. electronegativity increases from left to right.</p>

<p>Sparknotes says Br has higher electronegativiy.
i looked it up and it says kr has electronegativity higher than Br… which to trust</p>

<p>also what’s the difference between electronegativity and electron affinity</p>

<p><a href=“http://en.wikipedia.org/wiki/Electronegativity[/url]”>http://en.wikipedia.org/wiki/Electronegativity&lt;/a&gt;&lt;/p&gt;

7

<p>Kr is a noble gas. They are EXTREMELY unreactive. Br is halogen. Halogens are extremely REACTIVE. Br can fit one more electron into an orbital. Kr cannot.
Don’t think in raw numbers. Wikipedia may be technically correct, but I would doubt the test would say KR is answer, because Br is so much more reactive.</p>

8

<p>

</p>

<p>Sigma and pi bonds deal with how two atoms are bonded to each other. What to remeber is that a single bond has one sigma bond, a double bond- one sigma, one pi, and a triple bond- one sigma and two pi, and so on if that were possible. They don’t really have too much to do with molecular geometry and orbitals.</p>

9

<p>

I believe that electronegativity deals with how an atom acts when it is bonded to another atom, more specifically how much it attracts the electrons the atoms share in the bond. Electron Affinity deals with how much an atom wants to gain an electron/ how easy it is to do so. So EN- deals with molecules, EA-with atoms.</p>