Unit 5: Moles and Stoich

im off track and theres a math test in two days WHAT DO I DO HELLPP. its 5/11,... I hate moles and stoich. I hate chem in general

Why do we use moles?

Atoms cant be measured. Moles is the unit for amount

Avogadro's Constant

6.02 E23, in Section 2 molescules are in a mol

Mole calc:

grams/molar mass

Or

Mols of gas: volume/molar volume (constant at STP)

How to calculate Emperical formula

Calculate to mols, divide by smalles mols.

How to find molecular formula

Find emperical formula, take mass of moleuclar/emperical. mult this number by everything

Percent Composition of Percent by mass

part/whole times 100

% composition of water in a hydrate

(Mass of water/mass of hydrate) times 100

What is an anhydrate (its anhydrous)

water is removed

How to know all water has been taken out of hydrate?

Heat to a constant mass

Percent Yield

experimental/theoretical x 100

Why do we care about % yield?

Low yield means more waste

Green chemistry: we need high yields

Avogadro’s Law

Equal volumes of all gasses, when measured at the same temperature and pressure, contain an equal number of particles (moles)

Combined Gas Law

P1V1/T1 is equal to the final, P2V2/T2

Temperature must be in Kelvin

Boyles Law

At constant temperature, the volume of a gas is inversely related to the pressure

Charles Law and Gay-Lussac’s Law

Direct relationship, they each get rid of one thing off the combined gas laws.

Ideal Gas Equation!

PV=nRT

Pressure in Pa. Volume in cm3

n is moles. r is constant. Temp in Kelvin

crazy thing about Pvnrt

Pressure is in pa, so you x1000 if u need it in kpa

Volume is in cm3 so you /1000 if u need dm3

Temp NEEDs to be in Kelvin

Ideal gas MODEL

Gas particles have no intermolecular forces of attraction

volume of gas particles is negligible (lot of space in between)

Gasses have free moving particles