Chemistry

I wanted to know why carbon-12 was chosen as the atomic weight standard. Why did they change from oxygen in the first place?

Can someone please explain the following reactions? 1. Vitamin C titrated against acidified potassium permanganate The end point should be pale purple, but the pale purple keeps disappearing when vitamin C is added, later on, the solution turns brown instead of purple. 2. Excess acidified potassium permanganate + Vitamin C After standing in air for some time, the deep purple colour disappears, solution turns brown. If heated, purple fumes are given out, and small black solids, like little ants, are precipitated. Thank you!!

Does the molecular structure of a mineral express a "form" of information? If so, is crystallization a transfer of that information?

Hi to All Can any one suggest a process Carbon dioxide into calcium carbonate in a easy step?

What is the resonate frequency of Potassium Nitrate?

Hi, I really need help ! Is there anyone who could tell me if there are any standards which specifically tells you the proper procedures on how to carry out Thermal Shock test on plastic materials (Like Lens). Things like: 1) Number of cycles 2) Criteria to restart test (Percentage of interruption) Ive checked Mil Std & JEDEC standards but they do not provide any specific standards for Plastic materials. (Only Electronics) The above 2 standards however provided a general procedure but Im not really sure if it applies to plastic.

using only water, ice and one of the substances below, im suppose to lower the temperature of water as much as possible. I was given 10 substances and I have successfully lowered them down to 2 choices. So the substances left for me to choose are: 1. CaCl2 • 2H20 2. Na2Co3 Which substance should I mix with about 10mL of water+ice for it to reach a very low temperature? I know that the more ions the substance has the lower the water's temperature will become. But right now I'm confused between CaCl2•2H20 and Na2Co3. Any help please?

According to Avogadro's hypothesis,one mole of every substances occupy 22.4 litres. if we measure the volume of 17 gm of ammonia will it occupy such????

Basically, my friend and I conducted an experiemtn for 10th grade chem in which we used five liquids with different pH levels and measured the time it took for different liquids to dissolve a Jolly Rancher. I'm working on the final paper, and most of it is straight forward, but I can't find any information on the relationship between the pH of solvents and the time it takes to dissolve solutes. Does anyone know of any similar experiments or about the relationship (if there is one)? We found that the more alkaline solvents dissolve the candy faster, which wasn't what we expected. Does it depend on the solute? Can anyone help?

I need help in starting and setting up this prolem. I do not want the answer. The Queastion is: Determine the mass in grams,of 6.02 X 10^23 silver atoms (sorry)

Please, will someone help me to understand this? The literature describes removal of residual water from insoluble product by washing the product with concentrated salt water. Can someone explain the chemical mechanism by which this works? Thanks! imp

what causes the temperature increase?

How are napthalene balls made? What is it made of?

Can specially denatured alcohol (SDA) be substituted with water in making linen spray? Currently, i make it using SDA, Fragrance, Tween 20 (or 80), DPG, Fixative and add some water just to make it cost-effective. Is it possible to sub the alcohol w/ H2O w/ no negative effects on the end product?

I was wondering what people could tell me about coating glass, particularly windshield glass, to make it better. Normally, glass is somewhat hydrophilic, which is annoying because water droplets can form on it, and stick to it. --- Some examples that I know of: A coating of detergent left on glass will prevent fog from building up on the glass, eg on the inside of a windshield or on a bathroom mirror, by breaking the surface tension of water droplets. However, it will come off when washed, though it will stay for quite a while otherwise. A thin coating of titanium dioxide will make glass hydrophilic and also act as a catalyst for decomposition of organic compound…

Does anyone have a good site or source that deals with handling alpha emitting radiation sources.

Hi, I was pondering over this question and want you people to help me out: Why couldn’t the enthalphy of formation be found directly but by taking enthalpies of combustion first? I think it got to do with the time needed to measure the temperature. Any ideas!

Hi all! I was doing some past papers and I have some problem. The question was: Q. Alcohols and esters are important organic compounds which are widely used as solvents. Esters such as ethyl ethanoate can be formed by reacting carboxylic acids with alcohols. CH3CO2H + C2H5OH <------> CH3CO2C2H5 + H20 For this equilibrium, the value of Kc is 4.0 at 298K. A mixture containing 0.5 mol of ethanoic acid , 0.5 mol ethanol, 0.1 mol ethyl ethanoate and 0.1 mol water was set up and allowed to come to equilibrium at 298K. The final volume of the solution was V dm3. Calculate the amount, in moles, of each substance present at equilibrium. My…

why is sea water always salty????

Hi Is this some sort of a special effect or can you really do this? Also how do they do the voices? I get helium but what about the other thing? John

Is there any chemical that produces a white coloured flame when burning?

Anyone with some practical chem smarts can help me with this one. I have several questions about ozone production. Why are large voltages used in industrial ozone production? What determines the threshholds? If the threshholds are high, then why do small voltages---even household level or thereabouts---seem able to produce ozone in small amounts? I assumed that one energy requirement would be that needed to break the O=O bond and get atomic oxygen So I looked up the O=O molecule bond and found it was 498 kJ/mole so I put this into google 498 kJ/Avogadro's number/eV and it tells me that the bond is about 5.2 eV------around 5 electron volts. I …

Hi there I am a very unscientific person looking for some help in identifying certain traits of Beryllium. Specifically, I was wondering whether anyone could help me with the following 2 values: 1. Thermal shock resistance 2. Thermal expansion co-efficient (perhaps in E-6/K?) I am also trying to identify 2 other things: a measure of inertness, and thermal shock resistance for the following: 1. Silicon carbide 2. Quartz 3. Graphite 4. Silicon I hope this makes at least a modicum of sense. If anyone could help me in any way, even by pointing me in another direction, I would be very very grateful! thanks M

Ok, we are asked to find the energy required to remove the first electron on Li using Bohr's equation E= -2.179e-18 (Z) (1/n^2-1/n^2) where n is intial and final energy levels and Z is atomic number. I get 1.634e-18 J/ electron. I convert this moles and I get 9.84e5 J or 984 kJ/mol. But it asks to compare this value to the IE value for Li's first electron, which is 520 kJ/mol. It asks if these values are to be the same. I would assume so, but my math says otherwise. Did I mess up somewhere? Thanks in advanced. edit: Sorry didn't notice the homework help thread. But if any can help here that'd be nice >.<

My girlfriend has been asking me for awhile now about what the coldest temperature fire can be sustained at? Im not a chemist of anything but i figured this would be the right forum to ask it on. She thinks it paper burning at 451 degrees but i have no idea. Any help would be appreciated