How you explain the increase in weight in of the recovered material?
A student started an experiment with a mixture of sand, salt, and iron weighing 2.345g. After separating the components, a total of 2.765g of material was recovered. Assume that all the weighing and calculations were done correctly. How could you explain the increase in weight of the recovered material?
Can all compounds be electrolytically separated?
No. Not all compounds can be separated electrolytically - the classic examples of electrolysis are the production of Hydrogen & Oxygen gas from water, or Chlorine gas & Sodium hydroxide from brine.There are many other techniques to separate compounds and elements;Distillation; separation by boiling point. Used to fractionate air into its component parts (Nitrogen, Oxygen, Argon, Xenon, Krypton etc), crude oil (in order to make petrol, gases and other such materials) and also in very many types of organic synthesis.Separation by selective reactivity - for example, a sodium bisulfite solution can be used to separate aldehydes and ketones to form addition products or sulfonic acids which can then be filtered. Very useful technique in organic chemistry to extract a target molecule following a reaction. It can then be further purified by distillation.Crystallisation; using solvents or reagents with different solubility to separate compounds of differing polarity or chirality. Very commonly used in the pharmaceutical industry to obtain a particular isomer of a drug, or to purify salts of both inorganic and organic compounds. Crystallography and crystal growing are very important techniques in chemistry.Chromatography; using various techniques (thin layer, column, high pressure column, gas), almost always involving a moving and stationary phase (usually a solvent or gas, and a solid column (of Alumina or Silica). Extraordinarily useful for analytical and preparative chemistry.
Why can't most of the sedimentary rocks be dated radiomatically?
Firstly you are confusing Carbon Dating with other forms of radiometric dating. Carbon dating relies on measuring the balance of carbon isotopes in organic materials, and due to the relatively rapid decay of Carbon 14 can only be used to date items a few tens of thousands of years old, not the millions of years we need for geological dating. Other radiometric techniques use the much slower breakdown of radioactive elements found in rocks, such as Potassium->Argon or Uranium->Thorium. When these elements are molten, in magma the parent and daughter elements will get separated, but when the magma crystallises in many cases the parent and daughter elements are locked together in the same crystal structure, so their relative amounts can be measured. We can then use this to date when the rock crystallised, so we can use the technique to tell how long ago the rock solidified from its parent magma. Of course this only works for rocks that did solidify from magma i.e. Igneous rocks (and with some adaptation to metamorphic rocks). Sedimentary rocks are made up of fragments of pre-existing rocks, and if those fragments are suitable minerals derived from igneous rocks we can tell how old the rocks the fragments came from are, but *not* how long ago those rocks were broken down into sediment, not how long ago the sediments became lithified (turned into rock) as neither of these processes reset the radiological clock by separating the different radio-isotopes in the mineral.
Why do you think the noble gases are placed in a separate group?
Separate them how?In the Periodic Table of the Elements, they each have a separate location because they are each independent chemical elements and every element has a separate location in this Table.When chemists are using the elements, if is common practice to begin a process with pure materials rather than mixtures, so it would be appropriate to separate and sell the noble gases in pure form rather than as mixtures.
How can you separate oxygen and hydrogen in gas form, without changing the temperature?
Yes, there are materials that can be used to either allow hydrogen to pass, while blocking oxygen (http://pubs.acs.org/doi/abs/10.1...), or to adsorb the hydrogen, while allowing the oxygen to pass (http://www.sciencedirect.com/sci...).The thing is, though, these methods tend to be relatively expensive. They may make sense at small scales, but if you want to separate the two in bulk, cooling them down until the oxygen liquefies is probably the easiest way.As someone else mentioned, the most low-tech way to do it would be to burn the mixture, collect the resulting water, then separate it into hydrogen and oxygen with an electric current, and collect the gasses separately. That's massively inefficient, taking lots of time and huge amounts of energy, but it's something that can be done with common household materials.
What is the difference between elements,compounds and mixtures ?
elements - only contain one type of atom and the list of elements is the periodic table, i.e. O2 compounds - a mix of two or more atoms, i.e. H2O Mixture - combination of two or more compound/molecule... i.e. sand
Is it possible to isolate and bottle argon from atmospheric air using a shop compressor (max 150 PSI) and molecular sieve? There is a project on nitrogen isolation. What modifications would be required for argon isolation?
Q: Is it possible to isolate and bottle argon from atmospheric air using a shop compressor (max 150 PSI) and molecular sieve? There is a project on nitrogen isolation. What modifications would be required for argon isolation?The problem with this is that it’s one thing to isolate N2 when 78% of the air is N2. It’s another thing to separate out only argon (Ar) which is less than 1% or the atmosphere. Obviously it’s done, but normally through absorptive reactions.I’m familiar with using molecular sieves to remove water from ethanol to defeat the azeotrope. Using it in this circumstance would be problematic in that the Ar is mono-atomic where O2 and N2 are diatomic and all are from the same row of the periodic table, thus Ar is a smaller molecule. Molecular sieve is useful for removing smaller molecules from larger molecules, but here you have the reverse. The mole-sieve would be used to remove the Ar, not the N2, O2, CO2, etc.Could you use molecular sieves to remove Ar and then reclaim it from the beads? While probably technically possible… Let’s just say it’s outside the scope of your question and leave it at that.There’s not much I would call impossible, and I won’t call your quest impossible here, but that’s as far as I’m going to go into it.Here is a link to a scholarly paper (you’d have to purchase it) that talks about findings from a study using pressure swing adsorption to separate Ar from an Ar/O2 mixture. This is similar to but not exactly what you’re after, but you can read the abstract or even order it to learn more. Clearly, there is research but it doesn’t appear to be at the stage you need it to be.Production of Argon from an Oxygen−Argon Mixture by Pressure Swing Adsorption