MCAT General Chemistry Chapter 1

Question 1

Air

Answer 1

Contains the pure compounds nitrogen(~78%), oxygen(~21%), water vapor and other gases(~1%).

Question 2

Pure Compound

Answer 2

Made up of molecules which are composed of smaller units: the atoms, which combine in specific ratios to form molecules.

Question 3

Chemical Reaction

Answer 3

Molecules break down into individual or fragments of atoms which then recombine to form new compounds.

Question 4

Stoichiometry

Answer 4

Establishes relationships between atoms specific ratios for individual molecules or for molecules involved in a given chemical reaction

Question 5

Water

Answer 5

Not a mixture because the ratio is specific and does not vary with the location or the experimental conditions.

Question 6

Empirical Formula

Answer 6

Simplest whole number ratio between the numbers of atoms of the different elements making up the compound.
Ex. H2O empirical formula is 2:1 ratio

Question 7

Molecular Formula

Answer 7

Stated the exact number of the different atoms that make up this molecule.
Ex. H2O2 empirical formula is 1:1 ratio and molecular formula is 2:2 ratio

Question 8

Avogadro’s Number

Answer 8

The number of atoms in 12 grams of the most abundant isotope of carbon.
NA = 6.02 x 10^23

Question 9

Isotopes

Answer 9

Elements which are identical chemically since the number of protons are the same; their masses are slightly different because of different numbers of neutrons.

Question 10

Moles

Answer 10

A mole of atoms or molecules contain an Avagadro’s number (6.02 x 10^23).

Question 11

Gram-Atomic Weight

Answer 11

The weight in grams of a mole of atoms of a given element.
GAW sometimes measured in atomic mass units.
# moles = (wt. sample in grams)/GAW

Question 12

Gram-Molecular Weight

Answer 12

GMW the weight in grams of a mole of molecules of a given compound. 
# moles= (wt. of sample in grams)/GMW