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1. Concentrated H2SO4 is used as a catalyst in dehydration of ethanol to form ethene and water, we all know that. And that dilute H2SO4 can be used in hydration of ethene. But my teacher found some source saying that conc H2SO4 can used as a catalyst in hydration of ethene as well. Question is, why would you use conc if dilute suffices? Wouldn't you wanna save materials? Or are there any difference in how they aid the rate of reaction?
2. This one's weird. And bugging me for a while. If you've got ethanol, ethene, and conc H2SO4 mixed in a closed system and heated, what do you get? More ethanol, more ethene, or more butane? I've got a range of answers from people...
3. In general, solubility of solids (in water) increase with increasing temperature, but that of gases decrease. Why?
4. Why doesn't the value of the equilibrium constant change when volume or pressure (strictly speaking, gas partial pressure, and only for equilibria involving gases) or conc of reactants/products change? Why does it change with temperature?
5. In the first steps of the prac determining the sulfate content of a fertiliser, a few drops of HCl is added to the fertiliser dissolved in water, before it is heated and Ba2+ added blah blah blah... What's the HCl for? The teacher said it's basically to ionise/dissociate all constituent molecules into ions. I'm wondering how exactly does this work.
6. Tc-99m is used in medicine, and my teacher said that Tc-99 cannot be used. It's because of the long half-life of Tc-99 (which is something like >0.2 million years, compared to 6 hours of Tc-99m), which is a beta emitter. Problem though: Tc-99m decays into Tc-99 anyway, so what's the point? Or am I missing something?
7. Just wondering if anyone could explain what are geometrical and optical isomers, and what's the difference. I've wiki-ed them but I'd like a clarification
(Weird. A bazillion questions pop up when I look at chem. But when I look at physics, I just go, "Yep, yep, this all works..." Hey, I can't control the number of questions that come up in my head...)
2. This one's weird. And bugging me for a while. If you've got ethanol, ethene, and conc H2SO4 mixed in a closed system and heated, what do you get? More ethanol, more ethene, or more butane? I've got a range of answers from people...
3. In general, solubility of solids (in water) increase with increasing temperature, but that of gases decrease. Why?
I'm thinking that for gases, given more energy as temp increases, they would have a greater tendency to break the bonds with water molecules, and escape into the air. But why doesn't it work for solids? Dissolution in general is exothermic. Then why don't solids dissolve less in warmer water?
4. Why doesn't the value of the equilibrium constant change when volume or pressure (strictly speaking, gas partial pressure, and only for equilibria involving gases) or conc of reactants/products change? Why does it change with temperature?
This is my guess, someone see if it's on the right track: when the temp is changed, neither the total amount nor the conc of reactants/products are changed, but the position of the equilibrium is shifted, thus Keq is changed; looking at the expression of Keq and relate to (delta)H of the forward reaction, one can determine if the contant is increased or decreased. When the volume/pressure is changed, though, the conc of ALL chemicals in equilibrium changes, and it somehow shifts such that Keq remains the same. Same thing happens after the equilibrium shifts to counteract changes in conc of reactants/products. I'm not sure of the exact mechanism that makes Keq remain constant though. Someone give an explanation?
5. In the first steps of the prac determining the sulfate content of a fertiliser, a few drops of HCl is added to the fertiliser dissolved in water, before it is heated and Ba2+ added blah blah blah... What's the HCl for? The teacher said it's basically to ionise/dissociate all constituent molecules into ions. I'm wondering how exactly does this work.
6. Tc-99m is used in medicine, and my teacher said that Tc-99 cannot be used. It's because of the long half-life of Tc-99 (which is something like >0.2 million years, compared to 6 hours of Tc-99m), which is a beta emitter. Problem though: Tc-99m decays into Tc-99 anyway, so what's the point? Or am I missing something?
Could it be that beta particles Tc-99 emits are of low energies and thus of little harm to humans? And because of this, it's not useful in med cos you'd need easy detection of the radioisotope in the body? Still, surely you'd not wanna be exposed to beta particles, however low their energies might be...
7. Just wondering if anyone could explain what are geometrical and optical isomers, and what's the difference. I've wiki-ed them but I'd like a clarification
(Weird. A bazillion questions pop up when I look at chem. But when I look at physics, I just go, "Yep, yep, this all works..." Hey, I can't control the number of questions that come up in my head...)