chemistry 1- chapter 2
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.