Chemistry - Final

How to know if a molecule is polar?

How to know if a molecule is polar?

-Hydrogen attached to highly electronegative molecule

-Lewis structure lacks symmetry

How to know if a molecule is non-polar?

-1 element

-Monotomic/noble gas

-Molecule with hydrogen and carbon only

-Symmetrical lewis structures

Why is symmetry important in the concept of polarity?

Any structure that is symmetrical is ALWAYS non-polar

What are London Dispersion Forces and what kinds of molecules do they apply to?

-Relatively weak intermolecular forces that come from a briefly uneven distribution of electrons.

-Occur in ALL molecules, polar/non-polar/noble gases

-The only force of attraction between non-polar molecules/noble gases

What is a dipole-dipole bond and what kind of molecule does it apply to?

-The attractive force between positively charged end of a polar molecule and the negatively charged end of another polar molecule

-Not very strong forces

-Only occur between polar molecules

What is a hydrogen bond and what kind of molecule does it apply to?

-Strong type of dipole-dipole bonding which occurs when hydrogen is bonded with a highly electronegative atom

-Only occur between polar molecules

What is the formula for moles to grams?

number of moles x molecular mass = grams

What is the formula for grams to moles?

grams / molar mass = moles

What is the formula for moles to atoms?

(6.022 × 10 to the 23rd) x moles = atoms

What is the formula for atoms to moles?

number of atoms / (6.022 × 10 to the 23rd) = moles

What is the formula for mass percent?

total molar mass of just one element / molar mass of the whole compound x 100%

How to find empirical formula:

-Change the units given to moles

-Divide both by the smaller amount of moles

-Round the numbers found to whole numbers

-Apply those rounded numbers as coefficients for the compound

How to find molecular formula:

-Find molar mass of compound

-divide the given mass by the empirical mass

-Multiply the answer by the empirical formula

What is formula for moles to volume?

22.4 liters x number of moles = volume

How to find specific concentration:

Initial molarity x initial volume = final molarity x final volume

What are the signals that a chemical reaction has occurred?

-Color change

-Bubbles/release of gas

-Texture change

-Release of heat

How to find the limiting reactant?

-Balance the chemical equation

-Calculate the number of moles of each reactant

-Compare the mole ratios of the reactants to the mole ratio in the balanced equation

-Identify the reactant with the smallest value

How to calculate theoretical yield?

(number of moles of limiting reactant) x (molar mass of product) = theoretical yield in grams

How to find actual yield?

multiply the percentage and theoretical yield together

How to find percent yield?

divide the actual yield by the theoretical yield, then multiply the result by 100

How to calculate heat change?

the amount of heat gained or lost = the mass of the sample x the specific heat x the temperature change

How to convert joules to calories?

0.24 calories = 1 joule