Chapter 3, 4, and 5

Solve, using unit conversions when necessary, mass percent concentration problems. The basic algebraic equation has three variables. If any two of the variables are known, the third can be calculated.

(%m/m)=Mass of solute x 100% ___________________ Mass of solution I want a 27.83% NaCl solution. I need 225 g of solution . How much NaCl do I need? 27.83%= x x 100% _______ _________ 1 225 g 27.83% x 225 g = x x 100% ___________ __________ 100% 100% 62.6 g NaCl

Given a chemical formula, determine the number of individual atoms present and the total number of atoms present

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Calculate the empirical formula of any compound given the compound's percent composition

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Calculate the percent composition of a compound given its chemical formula

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Explain the difference between subscripts found in a chemical formula and coefficients found in a balanced chemical equation.

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How is a chemical equation written

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Identify a chemical reaction as either a combination (synthesis), decomposition, singledisplacement replacement), double-displacement (replacement), acid-base neutralization, or combustion reaction. Chemistry

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Interpret a balanced chemical equation in "mole terminology."

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List evidence for chemical reactions

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Understand the meaning of s, l, g, and aq as used in a chemical equation.

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Use the unit conversion method to calculate the number of atoms, molecules, units, etc. present in a specified quantity of material. (And the reverse calculation.)

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Using the guidelines to balance any type of chemical equation

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Binary compound

2 items/ in chemistry means 2 parts a compound containing atoms or ions of two elements.

Monatomic ion

1 atom an ion of a single atom.

Know that a mole (symbol mol) is a countable quantity and that

1 mol = 6.02 x 1023. Avogadro's number is 6.02 x 1023.

Calculate percent composition of a compound given mass data

1. First you find the atomic mass of the given compound NaOH Na= 22.99 g/mol O= 16.00 g/mol H=1.008 g/mol +_____________ 39.998 g rounded equals 40.000 g 2. You find the percent composition of each individual element %Na= 22.99 g x 100% ____________ = 57.475= 57.48% Na 40.00 g O%=16.00 g x 100% ____________ =40.00% O 40.00 g H%= 1.008 g x 100% ____________ = 2.52% H 40.00 g After adding all the percentages of each individual element of the compound the percentages should equal 100% 57.48% Na 40.00% O 2.52% H +_______ 100% NaOH If it all adds up to 100% then your answer should be correct!

calculate the empirical formula of any compound given the masses of different elements in the compound

A compound has 72.2% Magnesium and 27.8% Nitrogen by mass 1. Mg 72.2 g N 27.8 g 2. 72.2 g Mg 1 mol Mg ________ x ________ = 2.9699 Moles Mg 1 24.31 g Mg 27.8 g N 1 mol N ________ x _______ = 1.9842 Moles N 1 14.01 g N 3. Mg N 2.9699 mol 1.9842 mol 2.9699 mol Mg 1.9842 mol N ____________ ____________ 1.9842 mol N 1.9842 mol N =1.496 =1 4. 1.496 x 2 1 x 2 = 2.99 = 2 =3 =2 answer: Mg3N2 (This is the empirical formula)

Acid

A compound that releases Hydrogen ions when dissolved in water or donates H+ to another substance.

Molecular Formula

A formula that indicates the actual number of atoms present in a molecule

Solution

A solution contains a solute and a solvent solute + solvent = solution

What is the difference between a strong electrolyte and a weak electrolyte?

A strong electrolyte is a solute that completely, or almost completely, ionizes or dissociates in a solution to form a cation and anion. These ions are good conductors of electricity. A weak electrolyte is a substance when dissolved in water does not dissociate completely to form the cation and anion. These ions are poor conductors of electricity.

Chemical equation

An abbreviated representation of a chemical reaction consisting of chemical symbols and formulas

Percent composition

An expression of the percentage of the total mass due to each element in a compound

Molecular compound

Contains 2 or more non metals. ex: CH4 and C6H12012

Ionic compound

Contains a metal and a non metal or sometimes a metal and a group of non metals. Contains also a cation and anion ex:

Calculate the molecular formula of any compound given its empirical formula and its molar mass.

Find the molecular formula of an element who has an empirical formula of CH20 and a molecular formula mass of 180 g/mol. 1. You first find out what the atomic mass is of the given compound For example CH20 has an atomic mass of C=12.01 g/mol x 1 = 12.01 g H= 1.008 g/mol x 2 = 2.016 g 0= 16.00 g/mol x 1 = 16.00 g +__________ 30.026 g 2. Then you take 180 g and divide it by 30 and get 6. 3. 6 is the number of formula units that you will multiply by for ex: The empirical formula of the molecule is CH2O. The molecular formula of the compound is C6H12O6.

Concentration

How much is present how much solute is in the solution

Use the dilution equation, M1V1= M2V2, to solve dilution problems. The equation has four variables. If any three of the variables are known, the fourth can be calculated.

I have a 3.98 M NaOH 2.00 M NaOH and I'd like 500 mL how much of concentrate do I need? 3.98 M x V1 = 2.00 M X 500 mL V1 = 2.00 M X 500 ml ______________ 3.98 M V1= 251 mL

Mass to mol

If I have 27.82 g of K how many moles of K are present? 27.82 g K 1 mol K _______ x _______ = 0.711508951=0.7115 mol K 1 39.10 g K

Mol to mass

If I want 0.977 mol of K how many g of K needed? 0.977 mol K 39.10 g K __________ x ________ = 38.2007=38.2 g K 1 1 mol K

Dissociation

Ionic compound + water often will separate into the individual ions ex: NaCl + H2O = Na + Cl+ H2O ex: NaNO3 + H2O= Na+ NO3+H2O

Contrast ionic compounds and molecular compounds based on their physical properties

Ionic compounds are crystalline solids(made of ions), high melting and boiling points, conduct electricity when melted, many soluble in water but not in non polar liquid Molecular compounds are gases, solids, or liquids(made up of molecules), low melting and boiling points, poor electrical conductors in all phases, many soluble in non polar liquids but not in water

Solve, using unit conversions when necessary, molarity (molar concentration) problems. The basic algebraic equation has three variables. If any two of the variables are known, the third can be calculated.

M= mol KEY: 100 mL = 1 L ______ L I have 275 mL of a 3.28 M solution of KI. How many moles of KI are present? 3.28 M X 275 mL 1L ______= ________ = _______ x _______ = .275 L 1 .275 L 1 1000 mL 3.28 mol x .275 L _______ _______ = 0.902 mol KI L

Which class of element is usually positively charged?

Metals always have a positive charge.

Molecular mass

Molecular weight is a measure of the sum of the atomic weights of the atoms in a molecule.

Which class of element is usually negatively charged?

Non metals always have a negative charge.

Empirical formula

Observed The formula of a compound that has the smallest whole number ratio of elements in the compound ex: whole number ratio=subscripts =subscripts in a formula Mg3(PO4)2= Mg 3 P 2 O 8

Percent %

Parts per 100 Percent algebraic equation: Percent of part%= part x 100% ____________ total amount

Formula mass

The formula mass of a molecule is the sum of the atomic weights of the atoms in the empirical formula of the compound

Molar mass

The mass of 1 mol of any substance, in units of grams per mole

Molarity (M)

The number of moles of solute per liter of solution

Dilution

The process of adding more solvent to give a solution of lower concentration

Formula Unit

The smallest repeating unit in an ionic compound. Formula unit tells us the smallest whole # ratio of the atoms in that compound. Needs to be + to be an ion. ex: K+=Potassium ion K-= Potassium atom

Chemical reaction

a process in which one or more substances are converted into new substances that have compositions and properties different from those of the original substances

Reactants

a substance converted into another substance during a chemical reaction

Products

a substance formed from another substance or substances during a chemical reaction

non electrolyte

a substance that retains its molecular identity upon dissolving and does not conduct electricity when dissolved in water ex:table sugar in water, alcohol and kerosene.

Precipitate

an insoluble solid deposited from a solution

Polyatomic ion

an ion containing two or more atoms, ex: SO4-2

Determine the molar mass of any element or compound, g/mol or

g _____ 1 mol

Solvent

greater amount, the substance doing the dissolving

Electrolyte

is an ion dissolved in water, ions dissolved in water conduct electricity ex:Gatorade, ex of formulas that are strong electrolytes: NaCl, HNO3,HClO3, CaCl2

Solute

lesser amount, the substance being dissolved