Safety?

[khalil]

In every exam there is at least 'practical' question about chemistry, whether its reading of a burette or using safety procedures.

Learning this has led me to ask: Can someone outline the safety procedures in a laboratory? (My school never did this with us.)

Also, how would you safely neutralise 10ml HCl acid if it has spilled. One answer says to add water, but i thought we add an acid to water to avoid a explosion and not the other way around. And can't we just use any base to neutralise it?

[Edmund]

They are quite simple actually, you could come up with a few. Our school required us to draw up a table and note every hazards and precautions before every prac.

Safety gloves, goggles, lab coat, when handling chemicals.

Use of glassware: Be careful when handling, inform teacher if you break something.

No running, tie long hair, turn of gas taps when not in use.

If any chemical spills or chemical contact with eyes/skin, inform teacher/seek medical attention.

And yes, you can use a base to neutralise acid spills. We had a jar of powder for acid spills. (I think it was bicarbonate)

[/0]

In one of the trial exams it asked for safety precautions and the answer was to read up on the chemicals being used and note their hazards.

[Toothpaste]

Don't pipette with your mouth.

There's posters with this warning everywhere at uni :\
Has anyone even done it? haha

[Edmund]

Don't pipette with your mouth.

There's posters with this warning everywhere at uni :\
Has anyone even done it? haha

The older teachers probably did that back in the days when there weren't any pipette fillers...

[khalil]

They are quite simple actually, you could come up with a few. Our school required us to draw up a table and note every hazards and precautions before every prac.

Safety gloves, goggles, lab coat, when handling chemicals.

Use of glassware: Be careful when handling, inform teacher if you break something.

No running, tie long hair, turn of gas taps when not in use.

If any chemical spills or chemical contact with eyes/skin, inform teacher/seek medical attention.

And yes, you can use a base to neutralise acid spills. We had a jar of powder for acid spills. (I think it was bicarbonate)

Yer, but what kind of base?Cea says sodium carbonate...but why?

Also, by increasing the temperature in chromatography, how would that affect the retention time? Im guessing it will be higher cos there are more effective collisions between reactants, but CEA says otherwise.

[/0]

Increasing temperature means bonds will be weaker because temperature gives energy to break bonds. So there will be less adsorption to the stationary phase and hence lower retention time.

[khalil]

Increasing temperature means bonds will be weaker because temperature gives energy to break bonds. So there will be less adsorption to the stationary phase and hence lower retention time.

But if bonds were broken wouldnt that make them more reactive cos they'd want to attach to fill their shell?

Also, why is it when there is higher energy there is a short wavelength

[chem-nerd]

Also, how would you safely neutralise 10ml HCl acid if it has spilled. One answer says to add water, but i thought we add an acid to water to avoid a explosion and not the other way around. And can't we just use any base to neutralise it?

considering this sort of spill is small and probably a low concentration, diluting it with water would be suitable and not result in a highly exothermic, explosive reaction

normally though, you'd be better off using a spill kit which would contain some sort of absorbant solid mixed with sodium carbonate (which is a weak base). using a strong base is just as bad as the acid spill itself and it could result in an exothermic reaction. also it's difficult to tell when you've added enough.

[khalil]

Also, how would you safely neutralise 10ml HCl acid if it has spilled. One answer says to add water, but i thought we add an acid to water to avoid a explosion and not the other way around. And can't we just use any base to neutralise it?

considering this sort of spill is small and probably a low concentration, diluting it with water would be suitable and not result in a highly exothermic, explosive reaction

normally though, you'd be better off using a spill kit which would contain some sort of absorbant solid mixed with sodium carbonate (which is a weak base). using a strong base is just as bad as the acid spill itself and it could result in an exothermic reaction. also it's difficult to tell when you've added enough.

but how come we can do titrations with a strong acid and base? If a high exothermic reaction occurs than isn't it dangerous to do it in the first place?

[khalil]

Also, why low strength bond absorb lower energy than a higher strength bond.
why is it that the higher the mass the lower the energy of the radiation absorbed?

[Mao]

Also, how would you safely neutralise 10ml HCl acid if it has spilled. One answer says to add water, but i thought we add an acid to water to avoid a explosion and not the other way around. And can't we just use any base to neutralise it?

considering this sort of spill is small and probably a low concentration, diluting it with water would be suitable and not result in a highly exothermic, explosive reaction

normally though, you'd be better off using a spill kit which would contain some sort of absorbant solid mixed with sodium carbonate (which is a weak base). using a strong base is just as bad as the acid spill itself and it could result in an exothermic reaction. also it's difficult to tell when you've added enough.

but how come we can do titrations with a strong acid and base? If a high exothermic reaction occurs than isn't it dangerous to do it in the first place?

Strength and concentration aren't related. HCl is a strong acid, but the concentration it's used in a titration is usually around 0.1 M or less. Whilst the reaction is still exothermic, the amount reacting is small, hence its effects are small.

If you were to perform a titration using conc sulfuric acid (98% pure), which is both strong AND concentrated, the experiment would get a bit explosive.

[khalil]

A 0.360 g sample of an organic compound containing carbon, hydrogen and oxygen was burnt in excess oxygen. When the gases evolved were passed through anhydrous CaCl2 its mass increased by 0.216 g. The remaining gases, when bubbled through a NaOH solution, increased its mass by 0.528 g. The mass of oxygen in the sample is ...

[excal]

Forgive me for being a chemistry noob, but doesn't a greater pH difference between two reactants create a stronger neutralisation reaction? If that's the case, water would be safer than using bicarbonate soda...