<p>im not asking how to do it,but asking how to study for it.(dont get the wrong idea,im not asking for answer :P) </p>
<p>^^for #5c, they are asking for things like black precipitate,however,what chapter does this belong to.cuz i usually have trouble in doing problems related to the color of the precipitate.</p>
<p>I guess you’re talking about number 5?</p>
<p>A-You know they are testing how flamable the gas is because they are using a burned wood stick. Nitrogen doesn’t make it burn. I think hydrogen would give a loud “pop”, and it would probably make the flame red. Oxygen just make the wood stick burn (normal looking). </p>
<p>I didn’t look at the answer key on collegeboard, so you should check if I’m right. This question ask about these random little things that you should probably pick up somewhere (in labs most likely), and you just need to know these kind of things. </p>
<p>B- CO2 react with water to form H2CO3, which is a weak acid. Therefore the pH is less than 7.
SiO2 probably just dissolve in water by the polarity of water. No electron or charges involved. So pH is probably 7.
CaO form Ca2+ and O2- in water. The ions form a base. pH greater than 7.
As for this question, you should read something similar in the Acid/Base chapter.</p>
<p>C- (i) I say it’s Ag2S, because only Ag form a precipate. And Cl- compounds usually is not black. So that leaves the thing to Ag and S.
(ii) A precipate. Because Ag would form a precipate almost all the time.
(iii) There’s no way Ag would have no reaction, so solution 2 is not AgNO3. And that leaves AgNO3 as solution one. We determined that Ag2S is the black precipate, so Na2S is solution 2. That leaves the KCl as solution 3. </p>
<p>I say know solubility rules. And honestly, I just guessed on the Ag2S because Sulfur sounds like it would form a more colorful compound than Cl. I don’t think there’s a chapter on this kind of things, but you can always look at the pictures throughout the book to learn the colors of different things. </p>
<p>Hope this helped.</p>