chemistry 1- chapter 2

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how many moles are there in 55.2 grams of sulfur?

1.72 Moles S

what are compounds

Substance consists of two or more elements (H2O, C12H22O11)

The compd must be what?

Neutral NaCl sodium chloride (Na1+ & Cl1-) KOH potassium hydroxide (K1+ & OH1-) CaSO4 calcium sulfate (Ca2+ & SO42-) Al(OH)3 aluminum hydroxide (Al3+ & 3 OH1-)

What is the name of FeBr3? What is charge on both ions?

iron(III) bromide -Al3+ and SO42-

Percent Composition and Formulas of Compounds: % composition =

mass of an individual element in a compound divided by the total mass of the compound x 100%

We determine the empirical and molecular formulas of a compound from the

percent composition of the compound.-percent composition is determined experimentally

1 mole Cu = 63.55 grams (63.55 is the atomic mass)

29 Cu 63.55->Atomic Mass

The molar mass of propane, C3H8, is:

3 X C = 3 x 12.01 amu = 36.03 8 x H = 8 x 1.01 amu = 8.08 molar mass = 44.11 amu (g/mol)

What is charge on ammonium ion?

41+

1 mole =

6.022 x 10 23 "things"

what is the mass of 4.0 moles of sodium?

92 grams

Purity of Samples: The percent purity of a sample of a substance is always represented as

% Purity = mass of pure substance/mass of sample X 100 (mass of sample includes impurities

determine the percent composition of C and H in C3H8.

%C = mass C/mass C3H8 X 100

The Oxidation State of an atom in the free form (not combined) element = ?

0

Ex: A bottle of sodium phosphate, Na3PO4, is 98.3% pure Na3PO4. What are the masses of Na3PO4 and impurities in 250.0 g of this sample of Na3PO4?98.3% pure means? 250g sample x= 246 g Na3PO4 Calculate the mass of the impurities...

see Power point ch 2 p. 24

Ex: A compound contains 24.74% K, 34.76% Mn, and 40.50% O by mass. What is its empirical formula?•HINT!! Because we are dealing with PERCENTAGES...make the simplifying assumption that we have 100.0 g of compd.

see power point for ch 2 p. 19 and 20 and next examples

Empirical Formula is?

smallest whole-number ratio of atoms present in a compound

•Molecular Formula is ?

the actual numbers of atoms of each element present in a molecule of the compound -Ethene - C2H4 -Pentene - C5H10

what is a Mole (mol)

the amount of substance that contains as many atoms, molecules, or ions as are in exactly 12 g of carbon-12.

Formulas of ionic compound are determined by what?

the total charge on the anions.

Oxidation State: the Total (sum) of the oxidation states of all atoms in a molecule or formula unit = ? For an ion: total = ? For a compound: total = ?

0 the charge zero (no charge, neutral)

what are two basic types of ions:

1. Positive (+) ions or cations (Na+, Ca2+, Al3+•NH4+ (polyatomic cation) 2. Negative ions or anions•(F-, O2-, N3-•SO42-, PO43- (polyatomic anion) See Table 2-2

What is the formula of aluminum sulfate?

2(SO4)3

The number of formula units in a mole is known as

Avogadro's number.(Avogadro's number has been measured experimentally) Its value is 6.02214199 x 1023 formula units per mole.

the ratio of the elements present in the molecule or compound is the ______?

Chemical formula- it shows the chemical composition of the substance.

Table 2-1 gives names of several molecular compounds.-know these

Ex:H2SO4 - sulfuric acid FeBr2 - iron(II) bromide C2H5OH - ethanol

The molar mass is the atomic mass from the periodic table expressed in what?

Grams

What is the formula of nitric acid?

HNO3

what are some monatomic elements

He, Au, Na

The mass of one mole of atoms of an element is known as the element's what

Molar mass

what are some diatomic elements

O2, H2, Cl2

What is the formula of sulfur trioxide?

O3

what are some more complex elements

O3, S4, P8

Formula Weights, Molecular Weights, and Moles How do we calculate the molar mass of a compound?

add atomic weights of each atom

CH2 is the empirical formula for

alkenes No alkene exists that has 1 C and 2 H's

what are Ions

atoms or groups of atoms that possess an electric charge.

Occasionally, we will use millimoles. -Abbreviation: mmol -1000 mmol = 1 mol (just like 1000 mL = __1__ L)• Ex: oxalic acid (COOH)2-1 mol = 90.04 g -1 mmol = 0.09004 g or 90.04 mg

ex: oxalic acid (COOH)2 -1 mol = 90.04 g -1 mmol = 0.09004 g or 90.04 mg

A mole, whether it is a mole of iron atoms, a mole of methane molecules, or a mole of sodium ions, always contains the same number of what?

formula units

formulas of ionic compd are determined by

he total charge on the anions.


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