[neffy]

i just wana ask your help, mga chemists!
yesterday, we had r laboratory expeeriment and someof the questions there were not yet answered by me. i find it hard.

the question are:
>which is more suggested or beneficial is it using an LPG or an octane?
i have ans.bwt this but i think it is defective....i chose using octane because it's not an hazardous chemical rather than LPG..(can u give me the accurate or more like precise regarding with this matter?)

> what's with the charcoal, that made the flame reacted when it was sprayed it into the flame of the bunsen burner?
ans. because of the combustion present on it...?

pls. i need the answer before nextweek will approach..

[neffy]

what's the difference between taking volume readings of a colorless/clear liquid and an opaque liquid?

> i guess, this is about the measurement or volume readings of the meniscus in a different apparatus use such graduated cylinder or beaker.

case study:
EVAPORATION:
 
Why is it better to carry out evaporation by the use of a water bath?
>ans. for more concentration of the chemicals which is the sodium chloride and silver nitrate on the evaporating dish that is placed on a beaker filled with water. is that so?

can u give me atleast 3 precautions and reasons why these should be followed in the process of evaporation activity.

[neffy]

post questions:

1. why should objects never be weighed while still hot?
 
ans.maybe its a matter of observing or waiting for the reactions that may occur to that objects. can u add it?

2. can u cite the reasons for the use of glass-stoppered bottles for acids and plastic-stoppered bottles for bases.

ans. to free from danger and cautions. i think that's a precautionary measures. is that so?

3. why should excess chemicals never be returned to reagent bottles?

ans.it has been used already and maybe if u gonna returned it to reagent bottles those excess chemicals, there will be no reactive or used if it will gonna be perform in your next experiment.

4. which is more effective method of separation--decantation or filtration?

ans. the filtration, because it purifies the liquid more. on one hand, decantation is uncertainty because of its solid particles that is hard to transfer from one container to another.

[jdurg]

Okay, ease up there buddy.    First off, please don't post 8 million different threads.  If you have a bunch of questions, please try and keep them into one thread.  I've merged the three threads together into one so that it will be easier for people to help you out.  Also remember that it may take some time for people to get to your questions.  We're not paid here and we don't ask for donations, so we do all of this on our free time.  (Right now I'm helping you out during some free time here at work, so feel special.   )  Anyway, as you've at least shown that you've tried to attempt the questions, I'll try and give you a hand.

1. why should objects never be weighed while still hot?

ans.maybe its a matter of observing or waiting for the reactions that may occur to that objects. can u add it?

I'm not sure I understand your answer correctly, but from the interpretation I have you are correct.  When a sample is hot, it can react with the oxygen and other gases in the air around it.  This reaction will cause the mass of the object to increase.  In addition, the hot object may cause damage to the scale by warping or altering the mechanical parts of the scale that are responsible for making an accurate weight.

2. can u cite the reasons for the use of glass-stoppered bottles for acids and plastic-stoppered bottles for bases.

ans. to free from danger and cautions. i think that's a precautionary measures. is that so?

Both acids and bases are caustic, dangerous chemicals especially in their pure form.  They will both cause damage to your skin and have a high level of reactivity.  So why would you keep one in a plastic bottle and one in a glass bottle?  If they are both reactive, one of them must react with something that the other one doesn't.  Here's a hint; bases are stored in plastic stoppered bottles for the same reason that hydrofluoric acid (HF) is stored in plastic bottles.  

3. why should excess chemicals never be returned to reagent bottles?

ans.it has been used already and maybe if u gonna returned it to reagent bottles those excess chemicals, there will be no reactive or used if it will gonna be perform in your next experiment.

If you look on a reagent bottle, you'll see many labels on there describing exactly what's in it, how strong of a concentration it is, and other very important pieces of information.  If you take something from the bottle in which the contents have been analyzed to a great extent and place it in a glass beaker or some other container with numerous unknown substances on it and in it, what happens to the purity of the substance?  Now what happens if you rely on the purity of the reagent chemical for another experiment, but it was contaminated when stuff was put back in the container?

4. which is more effective method of separation--decantation or filtration?

ans. the filtration, because it purifies the liquid more. on one hand, decantation is uncertainty because of its solid particles that is hard to transfer from one container to another.

Correct.  Decantation is just pouring excess liquid off of the top of something.  When pouring that liquid out, you may accidentally remove the product you're trying to purify, or you may not get all of the liquid off.  When you filter, you collect ALL of the product and get rid of most, if not all, of the liquid.

[hmx9123]

Jdurg was nice enough to answer some of your questions, but he took the easy ones.  Here we go with the less intelligible questions.

>which is more suggested or beneficial is it using an LPG or an octane?

For what?  You can't use octane in your portable grill very effectively, and propane won't help your car go very far.  This question needs to be more specific.

> what's with the charcoal, that made the flame reacted when it was sprayed it into the flame of the bunsen burner?
ans. because of the combustion present on it...?

What in the world are you talking about?  You mention charcoal, then specify that it was the charcoal 'that made the flame reacted when it was sprayed...'  This is not just poorly written English like the rest of your post, but rather not English at all--this is not a sentence and I have no idea what you are asking with it.  Please take the time to at least write intelligibly.  We take the time to answer in a thoughtful and intelligible manner.

what's the difference between taking volume readings of a colorless/clear liquid and an opaque liquid?

> i guess, this is about the measurement or volume readings of the meniscus in a different apparatus use such graduated cylinder or beaker.

My guess is that this has to do with being able to see the meniscus on the liquid itself.  Since you can't line up the graduation lines when you look through the glass, you may not get as accurate of a reading as well.  The meniscus would be more difficult to see on an opaque liquid regardless of container.

Why is it better to carry out evaporation by the use of a water bath?
>ans. for more concentration of the chemicals which is the sodium chloride and silver nitrate on the evaporating dish that is placed on a beaker filled with water. is that so?

Again, the answer you give is not in English.  Fortunately the question is.  Think about this: how else besides a hot water bath do you evaporate things?  {hint: think heat}  Now think about what happens if you use an organic solvent, say, ethanol.  What do you know about organic solvents, in terms of their safety properties?  Why would it be bad to evaportate them in a manner other than a water (or oil, etc.) bath?  Also think about what happens when you cook spaghetti--the boiling water part.  Does the water stay still, or does it bubble and splatter?  What's that called in terms of chemistry?  How does that play into this evaporation question, specifically in terms of a bath vs. another method of evaporation?