Biochemistry___Lesson-3___Chapter 2.7 thru 2.9

Question 1

What do you call an atom or molecule with an electrical charge resulting from a gain or loss of one or more electrons?

Answer 1

Ion

Question 2

What type of chemical bond is caused by the transfer of an electron from one atom to another?

Answer 2

Ionic Bond

Question 3

What is a synonym for “ionic compound”?

Answer 3

Salt

Question 4

What type of chemical bond occurs between a partially positive hydrogen atom and a partially negative atom (usually oxygen)?

Answer 4

Hydrogen Bond

Question 5

What type of molecule has an unequal distribution of charges?

Answer 5

Polar Molecule

Question 6

What type of chemical bonds cause a molecule to be polar?

Answer 6

Polar Covalent Bonds

Question 7

What causes a polar covalent bond to form?

Answer 7

Unequal sharing of valence electrons to fill valence shells

Question 8

What causes two atoms to share valence electrons unequally?

Answer 8

1 atom has a much stronger electronegativity than the partner atom

Question 9

What do we call the process by which covalent bonds are broken and new covalent bonds are made to rearrange atoms into new molecules?

Answer 9

Chemical Reaction

Question 10

What do we call the starting material of a chemical reaction?

Answer 10

Reactants

Question 11

What do we call the material that results from a chemical reaction?

Answer 11

Products

Question 12

Draw the chemical equation for a hydrogen and oxygen combustion reaction using structural formula. Include partial charges and add 2 dots on each line.

Answer 12

Question 13

Draw an electron distribution diagram of an ion of Na and Cl to scale.

Answer 13

Question 14

Draw a water molecule hydrogen bonded to 4 other water molecules. Include partial charges. Hydrogen bonds are dotted lines and polar covalent bonds are solid lines.

Answer 14

Question 15

What would need to happen to a neutral atom to make it a positively charged ion?

Answer 15

Lose an electron

Question 16

What would happen to a neutral atom to make it a negatively charged ion?

Answer 16

Gain an electron

Question 17

What attraction creates an ionic bond that holds two ions together?

Answer 17

Opposite charges

Question 18

What determines the mass of an atom?

Answer 18

The # of protons and neutrons in the nucleus

Question 19

What determines the size of an atom?

Answer 19

The # of electron shells, which is determined by the number of electrons

Question 20

How many electron shells does a neutral Na atom have?

Answer 20

3

Question 21

How many electron shells does a positive ion of Na have?

Answer 21

2

Question 22

What is the molecular formula of water?

Answer 22

H2O

Question 23

Which atom in the water molecule is more electronegative?

Answer 23

O, oxygen

Question 24

What is a hydrogen bond?

Answer 24

A weak chemical bond between a slightly positive charge on hydrogen and a slightly negative charge on another atom.

Question 25

How strong is a hydrogen bond compared to a covalent bond?

Answer 25

Very week

Question 26

What is a polar molecule?

Answer 26

A molecule with an unequal distribution of charges.

Question 27

Is water a polar molecule?

Answer 27

Yes

Question 28

A water molecule could hydrogen bond with how many other water molecules?

Answer 28

4

Question 29

Distinguish between nonpolar covalent, polar covalent, ionic, and hydrogen bonds.

Answer 29

They are all the same in that they hold atoms or molecules together.

The covalent bonds are formed by the sharing of electrons to fill the valence shells of both atoms, but nonpolar covalent bonds share the electrons equally while polar covalent bonds share the electrons unequally (electrons are closer to the atom with the greater electronegativity giving that atom a slightly negative charge and the other atom a slightly positive charge).

Ionic bonds are like covalent bonds in that ions are created to fill the valence shells of both atoms, but in the case of ions the valence electrons are not shared, but instead are completely transferred to the atom with the greater electronegativity. The resulting ions are then held together by the attraction of opposite charge.

Hydrogen bonds are like ionic bonds in that the attractive force is between opposite charges, but in the case of hydrogen bonds the attraction is between partial charges (not full charges). Hydrogen bonds are also unlike ionic bonds in that the partial charges do not result from the transfer of electrons but result from the unequal sharing of electrons in polar covalent bonds. A partial positive charge (created by a polar covalent bond in one molecule), is attracted to a partial negative charge (created by a polar covalent bond in a different molecule).

Question 30

Describe the chemical reaction of photosynthesis and include the following ideas: Break chemical bonds. Form new chemical bonds. Matter not created or destroyed. Account for all atoms in the reactants and products. Account for all molecules in the reactants and products.

Answer 30

Molecular formula: reactants 6CO2 + 6H2O —> products C6H12O6 + 6O2
In photosynthesis, 6 carbon dioxide and 6 water molecules are the reactants that are used to make 1 sugar molecule and 6 oxygen molecules as the products. This is accomplished by breaking and forming chemical bonds to rearrange the atoms into different molecules, without destroying or creating any matter (atoms). This can be seen in the balanced reaction, which shows 6 carbon atoms, 18 oxygen atoms, and 12 hydrogen atoms in the reactants and the same number of each type of atom in the products.