KBC Questions and Quiz, Multiple Choice Questions and Answers
Displaying 341 to 350 of 2066 Questions. You are on Page No. 35 of total 207 pages
Question: What is the major component of this adhesive: woodworking glue also known as PVA glue?
Incorrect Answer
Correct Answer OK, so the "PVA" in the question probably gave this one away! PVA = poly (vinyl alcohol). PVA glue is a solution of the water-soluble polymer poly (vinyl alcohol). The solution is fairly viscous and when it dries, it gives a nice clear finish. PVA is also used to make the popular children's toy "Slime". All that needs to be done is mix a solution of PVA with a solution of Borax with a little bit of dye and voila - Slime! Well, it's not quite that simple, but that's the general idea. The borax makes cross-links between PVA molecules, making much larger molecules that are even more viscous than the original PVA solution.
Correct Answer "Dry ice" is solid carbon dioxide (CO2). Carbon dioxide freezes at -78.5 degrees Centigrade. When dry ice "melts" it undergoes a process called sublimation. This means that it is converted from a solid directly to a gas, bypassing the intermediate liquid stage. This is where the name "dry ice" comes from - when it melts, you never get any liquid (unlike water ice), hence it's "dry".
Question: Nail polish remover is something that us girls just can't do without. But what exactly is it in nail polish remover that does the polish removing?
Incorrect Answer
Correct Answer Nail polish remover has acetone as a major component. Acetone is an excellent solvent - in my experience as a chemist, I've found it dissolves pretty much all organic (carbon-based) chemicals! Of course, there are exceptions, but when I want to clean my glassware, acetone is the solvent of choice! So when you use nail polish remover containing acetone, all it's doing is dissolving the nail polish so you can wipe it away. You can also buy "acetone-free" nail polish remover; this contains another chemical called ethyl acetate which works in just the same way.
Question: Bleach is another useful household chemical. It is often referred to as "chlorine bleach". What is the main component of household bleach?
Incorrect Answer
Correct Answer Household bleach is a 3-6% solution of sodium hypochlorite (NaOCl) in water. There is no actual "chlorine" (Cl2) in bleach at all, although it does contain a chlorine atom (Cl). Sodium hypochlorite is, however, prepared from chlorine (Cl2) and sodium hydroxide (NaOH), which is perhaps where the name "chlorine bleach" comes from. It is a very useful chemical in that it not only kills germs, but is also an excellent stain remover. Under normal household use, sodium hypochlorite breaks down into sodium chloride (table salt), oxygen and water, and has been recently found by the Swedish Environmental Research Institute to pose no environmental problems provided it is used in the correct manner. (Thanks to howstuffworks.com - an incredibly interesting website. If you haven't checked it out, make sure you've got a spare hour or three when you do go have a look!)
Question: Most people have used superglue at one stage or another, but what is its major chemical component?
Incorrect Answer
Correct Answer Superglue is a solution of a chemical called alpha-cyano acrylate. This chemical undergoes a process called anionic polymerisation, and this is what forms superglue. When you squeeze some superglue from the tube, anionic polymerisation of alpha-cyano acrylate is initiated by small amounts of water on the surface of the object (and on fingers also! ;)), and this leads to the rapid formation of the polymerised version of the chemical. Superglue is immensely strong - one drop can support 2000lb (900kg)! If you ever find yourself in a sticky situation with superglue, try using some acetone to dissolve it.
Question: Methylated spirits is a very common household chemical - but what is its main component?
Incorrect Answer
Correct Answer Methylated spirits is basically ethanol (ethyl alcohol). The "methylated" part comes from the fact that a small percentage of methanol (methyl alcohol) is added to pure ethanol to stop it from being used to make alcoholic drinks (!). Methanol is very poisonous, unlike ethanol which, although toxic in large quantities, does not have the toxicity of methanol.
Question: Which element has close to 10,000,000 known compounds?
Incorrect Answer
Correct Answer Carbon is unique among the elements in the vast number and variety of compounds it can form. With hydrogen, oxygen, nitrogen, and other elements, it forms a very large number of compounds, carbon atom often being linked to carbon atom. There are close to ten million known carbon compounds, many thousands of which are vital to organic and life processes.
Question: What element's three isotopes have different names?
Incorrect Answer
Correct Answer The ordinary isotope of hydrogen, H, is known as Protium, the other two isotopes are Deuterium (a proton and a neutron) and Tritium (a protron and two neutrons). Deuterium and Tritium are both used as fuel in nuclear fusion reactors. One atom of Deuterium is found in about 6000 ordinary hydrogen atoms.
