CHAPTER 2 REVIEW

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.

Which of the following statements about chemical bonds is true?

Covalent bonds are stronger than ionic bonds.

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 one hundred times more acidic than orange juice. This means that lemon juice has a one hundred-fold greater concentration of hydrogen ions.

CH4 is methane. This compound is ________.

organic

Once dietary fats are digested and absorbed, why can they not be released directly into the bloodstream?

All lipids are hydrophobic and unable to dissolve in the watery environment of blood. They are packaged into lipoproteins, whose outer protein envelope enables them to transport fats in the bloodstream.

Which of the following is a molecule, but not a compound?

H2

. C6H12O6 is the chemical formula for a ________.

hexose monosaccharide

The most abundant elements in the 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 percent of the mass of the human body, and the body cannnot make elements, so it is helpful to have them in consumables

Nitrogen has an atomic number of seven. How many electron shells does it likely have?

two

________ reactions release energy.

Catabolic, exergonic, and decomposition

. 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.

During a party, Eli 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, like any acid, releases hydrogen ions in solution. As excessive H+ enters the digestive tract and is absorbed into blood, Eli's blood pH falls below 7.35. Recall that bicarbonate is a buffer, a weak base that accepts hydrogen ions. By administering bicarbonate intravenously, the emergency department physician helps raise Eli's blood pH back toward neutral.

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?

Recall that the greater the surface area of the reactants, the more quickly and easily they will interact. It takes energy to separate particles of a substance. Powder and liquid laundry detergents, with relatively more surface area per unit, can quickly dissolve into their reactive components when added to the water.

Ty is three years old and as a result of a "stomach bug" has been vomiting for about 24 hours. His blood pH is 7.48. What does this mean?

Ty's blood is slightly alkaline

In a hurry one day, you merely rinse your lunch dishes with water. As you are drying your salad bowl, you notice that it still has an oily film. Why was the water alone not effective in cleaning the bowl?

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. Oils are nonpolar, and are repelled by water.

Which of the following is a functional group that is part of a building block of proteins?

amino

When an atom donates an electron to another atom, it becomes

an ion

The smallest unit of an element that still retains the distinctive behavior of that element is an ________.

atom

Uracil ________.

contains nitrogen, is a pyrimidine, is found in RNA

AB→A+B is a general notation for a(n) ________ reaction.

decomposition

. In DNA, nucleotide bonding forms a compound with a characteristic shape known as a(n) ________.

double helix

. What organic compound do brain cells primarily rely on for fuel?

glucose

A phospholipid ________.

has both polar and nonpolar regions

Which of the following combinations of atoms is most likely to result in a chemical reaction?

hydrogen and hydrogen

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 to donate one or more electrons?

magnesium's 12 electrons are distributed as follows: two in the first shell, eight in the second shell, and two in its 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

On the periodic table of the elements, mercury (Hg) has an atomic number of 80 and a mass number of 200.59. It has seven stable isotopes. The most abundant of these probably have ________.

more than 80 neutrons each

AB+CD→AD+BE Is this a legitimate example of an exchange reaction? Why or why not?

not an legitimat exchange reaction- components of thr eactants are identical to the componenets of the roducts. A component present among the reactants cannot disappear, not can a component not present in the reactants suddently appear in the products

. A pentose sugar is a part of the monomer used to build which type of macromolecule?

nucleic acids

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.

oxygen has eight protons. in its mosdt abundant stable form, it has eight neutrons, too, for a mass number of 16. in contrast 17O has nine neutrons and 18 O has 10 neutrons

Together, just four elements make up more than 95 percent of the body's mass. These include ________.

oxygen, carbon, hydrogen, and nitrogen

A molecule of ammonia contains one atom of nitrogen and three atoms of hydrogen. These are linked with ________.

polar covalent bonds

The energy stored in a foot of snow on a steep roof is ________.

potential energy

The characteristic that gives an element its distinctive properties is its number of ________.

protons

Chewing a bite of bread mixes it with saliva and facilitates its chemical breakdown. This is most likely due to the fact that ________.

saliva contains enzymes

. A substance dissociates into K+ and Cl- in solution. The substance is a(n) ________.

salt

A substance formed of crystals of equal numbers of cations and anions held together by ionic bonds is called a(n) ________.

salt

. Which of the following is most likely to be found evenly distributed in water in a homogeneous solution?

sodium ions and chloride ions

The ability of an enzyme's active sites to bind only substrates of compatible shape and charge is known as ________.

specificity

Jenny mixes up a batch of pancake batter, then stirs in some chocolate chips. As she is waiting for the first few pancakes to cook, she notices the chocolate chips sinking to the bottom of the clear glass mixing bowl. The chocolate-chip batter is an example of a ________.

suspension

The bonding of calcium, phosphorus, and other elements produces mineral crystals that are found in bone. This is an example of a(n) ________ reaction.

synthesis