Chapter 2
Explain why CH4 is one of the most common molecules found in nature. Are the bonds between the atoms ionic or covalent?
(A carbon atom has four electrons in its valence shell. According to the octet rule, it will readily participate in chemical reactions that result in its valence shell having eight electrons. Hydrogen, with one electron, will complete its valence shell with two. Electron sharing between an atom of carbon and four atoms of hydrogen meets the requirements of all atoms.) The bonds are covalent because the electrons are shared. Although hydrogen often participates in ionic bonds, carbon does not because it is highly unlikely to donate or accept four electrons.
Once dietary fats are digested and absorbed, why can they not be released directly into the bloodstream?
Dietary fats are digested and absorbed with the help of enzymes before getting released into the bloodstream as bigger particles cannot be absorbed. The fats are made of single fatty acid and three fatty acid chains bonded to a single molecule named glycerol. Fats can be harmful as well as beneficial. Saturated and Trans fats are harmful dietary fat whereas mono and poly saturated fats are beneficial.
Could two atoms of oxygen engage in ionic bonding? Why or why not?
Identical atoms have identical electronegativity and cannot form ionic bonds. Oxygen, for example, has six electrons in its valence shell. Neither donating nor accepting the valence shell electrons of the other will result in the oxygen atoms completing their valence shells. Two atoms of the same element always form covalent bonds.
AB+CD -> AD+BE is this a legitimate example of an exchange reaction? Why or why not?
It is not. An exchange reaction might be AB+CD -> AC+BD or AB+CD -> AD+BC. In all chemical reactions, including exchange reactions, the components of the reactants are identical to the components of the product. A component present among the reactants cannot disappear, nor can a component not present in the reactants suddenly appear in products.
The pH of lemon juice is 2, and the pH of orange juice is 4. Which of these is more acidic, and by how much? What does this mean?
Lemon juice is 100 times more acidic than orange juice. This means that lemon juice has a one hundred-fold greater concentration of hydrogen ions.
During a partyEli loses a bet and is forced to drink a bottle of lemon juice. Not long thereafter, he begins complaining of having difficulty breathing, and his friends take him to the local emergency room. There, he is given an intravenous solution of bicarbonate. Why?
Lemon juice is acidic. When Eli drank the bottle of lemon juice it made its blood too acidic which made his respiratory system compensate for the blood acidity to increase respiration but it was not enough. Therefore, the immediate action of the emergency room was to administer the bicarbonate solution intravenously to counteract the acidity of the blood since bicarbonate in an alkaline solution.
Magnesium is an important element in the human body, especially in bones. Magnesium's atomic number is 12. Is it stable or reactive? Why? If it were to react with another atom, would it be more likely to accept or donate one or more electrons?
Magnesium's 12 electrons are distributed as follow: two in the first shell, eight in the second shell, and 2 in the valence shell. According to the octet rule, magnesium is unstable (reactive) because its valence shell has just two electrons. It is therefore likely to participate in chemical reactions in which it donates two electrons.
If the disaccharide maltose is formed from two glucose monosaccharides, which are hexose sugars, how many atoms of carbon, hydrogen, and oxygen does maltose contain and why?
Maltose contains 12 atoms of carbon, but only 22 atoms of hydrogen and 11 atoms of oxygen, because a molecule of water is removed during its formation via dehydration synthesis.
When you do a load of laundry, why do you not just drop a bar of soap into the washing machine? In other words, why is laundry detergent sold as a liquid or powder?
Powder and liquid detergents have more enzymes and surfactants that work on grease and slime on the clothes. It is also easier for the molecules of the powder and liquid soaps to play its role as nonionic surfactants due to more freedom of its movement than that of a solid bar soap.
Oxygen, whose atomic number is eight, has three stable isotopes: 16O, 17O, and 18O. Explain what this means in terms of the number of protons and neutrons.
The atomic number of an element is the number of protons in an isotope. The number of neutrons is the difference between the mass and the atomic number 16= 8 protons + 8 neutrons 17= 8 protons + 9 neutrons 18= 8 protons +10 neutrons
The most abundant elements in foods and beverages you consume are oxygen, carbon, hydrogen, and nitrogen. Why might having these elements in consumables be useful?
These four elements - oxygen, carbon, hydrogen, and nitrogen - together make up more than 95% of the mass of the human body, and the body cannot make elements, so it is helpful to have them in consumables.
In a hurry one day, you merely rinse your lunch dishes with water. As you are drying your salad bowl, you notice a that it still has an oily film. Why was the water alone not effective in cleaning?
Water is a polar molecule. It has a region of weakly positive charge and a region of weakly negative charge. These regions are attracted to ions as well as to other polar molecules. Oil is nonpolar, and are repelled by water.
