Exam 2: Water and Carbon: the Chemical Basis of Life

The first chemicals that provided potential energy on Earth may have been formaldehyde and hydrogen cyanide. While these were produced by sunlight- driven reactions, they also occur around deep- sea vents. If the first organisms on Earth evolved around these vents, the first life on Earth was

What holds electrons in a covalent bond?

Which of the following unique properties of water is responsible for explaining how water can move from the roots of plants to their leaves against gravity?

Nitrogen N) normally forms only three covalent bonds because it has a valence of five. However, ammonium has four covalent bonds, each to a different hydrogen H) atom H has a valence of one). Make a sketch of this molecule. Count the number of electrons in your sketch. Compare this number to the number of valence electrons in one N and four H's. What is the charge on this molecule most likely to be?

Many scientific probes sent to other parts of the solar system are looking for signs of something so far known to exist only on Earth, namely

If an atom has a charge of +1, which of the following must be true?

Carbon is an important element for biology because

Which of the following tends to make chemical reactions spontaneous?

The structural formula for a certain molecule includes a group symbolized - O. The dash next to the oxygen atom means that a single bond exists to another atom, such as a carbon. Based on the valence of oxygen and the number of bonds it normally forms, what is the charge on the oxygen atom in this case?

The slight negative charge at one end of one water molecule is attracted to the slight positive charge of another water molecule. What is this attraction called?

Ice melts spontaneously at room temperature, even though the process is endothermic. How is this possible?

Which of the following is a violation of the first law of thermodynamics?

How can you determine the approximate mass of an atom in atomic mass units?

You need to write down information about a molecule, but need to indicate only which atoms it contains and how many of each. Which representation would work best?

The cities of Portland, Oregon, and Minneapolis, Minnesota, are at about the same latitude, but Minneapolis has much hotter summers and much colder winters than Portland. Why? Portland is near the Pacific Ocean; Minneapolis is near a number of large lakes.)

There are four elements that make up 95% of all matter found in organisms. Which of the following is not one of these?

Which of the following models is described by the idea that dissolved gases came in contact with minerals lining the walls of deep- sea vents and formed more complex organic molecules?

How many times can humans be sure the switch from nonlife to life has happened in the universe?

A solution with a pH of 5 has how many more protons in it than a solution with a pH of 7?

In the Gibbs free- energy relationship, why is the T term necessary?