Chemistry Mid-term (semester spring)

Crystal

Crystal

Trillions of ions arranged in a repeating alternating pattern:  Cation-anion-cation-anion-cation-anion…It could be the 3D-shaped structure of ionic bondings or metals.

Representative particles

The smallest unit in which a substance naturally occurs.

Mole

The SI unit for amount of substance:  The amount of substance that contains the same number of representative particles as there are atoms in 12 g of carbon-12, i.e.,

6.02 x 1023

Atom

The representative particle for elements is the ________.

Molecule

Two or more atoms covalently bonded together (may be same type of atom, e.g., O2, or different types, e.g. H2O).

Formula unit

The representative particle for ionic compounds is the ________.

Element

A kind of atom / a substance made entirely from one kind of atom, e.g., silver, or hydrogen.

Compound

Any substance containing two or more kinds of atom chemically bonded together, e.g water and salt.

Molecule

The representative particle for molecular compounds and diatomic elements (e.g., O2, H2 and Cl2) is the ________.

Atom

The building blocks of matter, made of protons, neutrons and electrons.

6.02x10^23

Avogadro’s number

N(A)

The symbol of Avogadro’s number

x^(5+2)

Multiply the coefficient

x^(6-5).y^(7-3)

Divide the coefficient

m = n * M

Calculating the mass of a substance

M = n * m

Calculating the molar mass of a substance

n = m / M

Calculating the number of mole of a substance

V = n * 22.4

Calculating the volume of a gas

n = V / 22.4

Calculating the number of mole of a gas

Avogadro’s hypothesis

Amedeo Avogadro suggested that equal volumes of gas, at the same temperture and pressure, contain the same number of particles. In other words, the volume of 1 mole of any gas is always the same.

22.4

The molar volume of a gas

n = N / 6.02x10^23

The calculation of number of moles of the representative particles

N = n * 6.02x10^23

The calculation of the number of representative particles

N * total number of atom

The calculation of the total number of atom

(mass of one element in one mole of compound / mass of compound) * 100%

The calculation of the percent composition of a substance