Chem Exam 1
% Oxygen atoms in Ca(NO3)2
# of Oxygen atoms/# atoms total 6 Oxygen atoms/ 9 total atoms x 100% = 66.6667% Oxygen
% (v/v) % (w/v) % (w/w)
% (v/v) = measured volume/total volume x 100 % (w/v) = measured mass / total volume x 100 % (w/w) = measured mass / total mass x 100
% Ca (w/w) in Ca(NO3)2
% (w/w) = measured mass / total mass x 100 Ca 1 x 40.1 = 40.1 g/mol Ca(NO3)2 molecular mass: 1641 g/mol 40.1 g/mol / 1641 g/mol= 0.024436 = 24.436 = 24.4%
There is a 12.04 g sample of a liquid compound of carbon, hydrogen and nitrogen that shows it contains 7.34 g C, 1.85 g H, 2.85 g N. What is the % composition?
% composition = measured mass/total mass x 100 % carbon = 7.34 g C/12.04 x cmpd x 100 =0.609 = 61% C % Hydrogen = 1.85 g H/12.04 cmpd = 0.1536 = 15.4% H % Nitrogen = 2.85 g N/12.04 g cmpd x 100 =0.2367 = 23.7%
1 mole
6.02 x 10^23/mol
A liter of air contains 9.2×10−4 mol argon. What is the mass of Ar in a liter of air?
9.2×10−4 mol argon (39.95 g/mol) 0.04 g/Ar
Universe is made up of
90% hydrogen 9.9% helium 0.1% everything else
How do you know you made something new?
Physical and chemical properties have changed
What type of change is pure substance to mixture and vice versa?
Physical change
absolute zero
The temperature at which no more energy can be removed from matter (have stuff, but not energy)
How many of C4H10 molecules are contained in 9.213 g of this compound? How many Hydrogen atoms?
Calculating molecules: mass of C4H10 / molar mass x avogadro's no molar mass: 58.14 g/mol 9.213 g (mol/58.14g)(6.02x10^23 molecule/mol) = 9.545x10^22 C4H10 molecules Calculating no of hydrogen atoms: H10 9.545x10^22 C4H10 molecules x (10C atoms/1 C4H10 molecule) = 9.545 x 10^22 hydrogen atoms
What does solids do when heated?
Expands fast and density decreases when heated
melting/freezing point
Freezing: 32F 0C Melting" 212F 100C
Condensation
Gas to liquid
What is the molar mass of H+? How much moles + atoms are there in H+?
H+ = 12.01 amu + 12.01 g/mol # of atoms and mole = 6.022 x 10^23
Calculating no of molecules and atoms from the mass of a compound
Molecules: We calculate the no. of molecules by first, getting the number of moles and then multiplying that with Avogadros no. mass of substance / molar mass x avogadro's no. g (mol/g) (6.02 x 10^23 molecule/mol) =molecules Calculating atoms: molecules derived from equation above x no of C atoms/element molecules (no of C atoms/molecule) = atoms
How do you know you have stuff in your hand?
it has mass and volume
What does all stuff have?
mass (weight) and volume (takes up space)
How many C4H10 molecules are contained in 9.213 grams of this compound? How many hydrogen atoms are there?
mass of C4H10 (g) / molar mass (mol/g) x avogadros no. (6.02 x 10^23 molecule/mol) Calculated molar mass of C4H10: 58..12 g/mol 9.213 g C4H10 (mol C4H10/58.12 g C4H10)(6.02 x 10^23 molecule/mol) =9.545 x 10^22 How many hydrogen atoms? H10 9.545 x 10^22 C4H10 molecule (10 C atoms/ C4H10 molecule) = 9.545
calculating no of atoms from mass of an element
mass of atoms (g) / molar mass (mol/g | derived from amu) x avogadros no. (6.06 x 10^23 atom/mol)
calculating moles from grams
mass of atoms (in grams) / mass of moles (mol/g) g x (mol/g) grams cancel out, and you're left with mol
At the US Department of Agriculture, the estimated averagerequirement for dietary potassium is 4.7 g. What is the estimated average requirement of potassium in moles?
mass of atoms (in grams) / molar mass 4.7 g K* (mol K/39.10g) = 0.12 mol K obtain molar mass by checking Potassium's amu; amu=molar mass
percent composition formula
mass of element/mass of compound x 100% used to figure out how much of each element is in a compound
physical property
mass, density, color, melting point you see physical changes
Universe
matter and energy (stuff and how it changes)
Matter can be further classified into
mixture and pure substance (elements + compounds)
calculating grams from moles
moles of substance (mol) x molar mass of compound (g/mol) mol x (g/mol) moles cancel out and you're left with grams
Property avg
avg= fA * pA + fB * pB (mass avg, density avg, etc) can be used to figure out fraction/compositions, and if so will need... x+y=1 y=1-x (also called isotopic abundance*isotope mass)
Mixtures
homogenous: same composition (sports drink | salt water) heterogenous: composition varies (salad dressing | rock + water)
Aristotle
hypothesized 4 elements: fire, water, air, earth
Conclusion of Rutherford's gold foil experiment
presence of a dense positively charge nucleus
2 types of observations
qualitative and quantitative
Sublimination
solid to gas
Properties of matter
solid, liquid, gas
Properties of solids, liquids, and gases
solid: definite shape + volume (particles stuck together and fixed in place) liquid: indefinite shape + definite volume (particles stuck together, but not fixed in location) gas: indefinite shape and volume (particles in motion, take up more space)absolut
formula mass
the sum of the average atomic masses of all the atoms represented in the formula of any molecule, formula unit, or ion referred to as molecular mass for covalent cmpds and ionic
Formula mass for Al2(SO4)3
write in simpler format Al2S3O12 Al - 2 x 26.98 = 53.96 S - 3 x 32.06 = 96.18 O - 12 x 16.00 = 192 53.96 + 96.18 + 192 =342.14 (ionic formula mass)
density of water
1.00 g/ml
A prospector panning for golf in a river collects 15.00 g of pure gold. How many Au atoms are in this quantity of gold?
15.00 g Au (mol/197.0g Au) x 6.02 x 10^23 atoms/mol Au= 4.585 x 10^22 atoms
Formula/molecular mass for CHCl3 (chloroform) C: 12.01 amu H: 1.008 amu Cl: 35.45 amu
C: 12.01 amu x 1 H: 1.008 amu x1 Cl: 35.45 amu x 3 12.01 + 1.008 + 106.35 = 119.37 amu
If 0.850 L of a 5.00 M solution of copper and nitrate Cu(NO3)2 is diluted to a volume of 1.80 L by addition of water What's the molarity of the solution?
C1 + V1 = C2 + V2 C2= C1 x V1/ C2 C= molarity V = volume
What volume of 1.59 M KOH is required to prepare 5.00 L of 0.100 M KOH?
C1 + V1 = C2 + V2 V1 = C2 x V2 / C1 C= molarity V = volume
What volume of 0.12 M HBr can be prepared from from 0.011L of 45 M HBr?
C1 + V1 = C2 + V2 V2 = C1 x V1 / C2 C= molarity V = volume
What type of change is elements to compounds and vice versa?
Chemical change
When metal bends slightly, it's because
It's a (+) charge and heavy.
Concentrations of diluted solutions
M1 + V1 = M2 + V2 M= molarity V = volume
Determine the % composition of C9H804.
Step 1: Determine total mass for each element and molecular weight. C9 x 12.01 = 108.09 g/mol H8 x 1.008 = 8.064 g/mol O4 x 16.00 = 64.00 g/mol Molecular weight: 180.15 g/mol Step 2: Find % composition: % composition = measured mass/total mass x 100 C = 108.09g C/180.15 cmpd x 100 =0.6 = 60.00% H = 8.064g H/180.15 cmpd x 100 =.044762 = 4.476% O = 64.00g O/180.15 cmpd x 100 = 0.35525 = 35.53%
A sample of compound contains 1.71 g C and 0.287 g H. Determine the chemical formula.
Step 1: Find moles for each element. 1.71g C (mol/12.01 g) = 0.142 mol C 0.287 g H (mol/1.008g H) = 0.285 mol H C0.142 molH0.285 Step 2: Divide each subscript by the smallest subscript. C: 0.142 mol C/0.142 mol C =1 H: 0.285 mol H/0.142 mol C =2 Chemical Formula: CH2
molar mass
The mass of one mole of a substance in grams (g/mol); it is numerically equal to the formula weight in atomic mass units.
nonmetals
brittle, dull, bad conductors, liquid/gas; low density, melting point, and boiling point
Chemical Properties of Matter
burn, rust, makes something new, reacts with O2
Compound examples
carbon dioxide, water, sugar
quantitative measurements
distance, energy, temp, time, mass, count, volume
When metal bends a lot, it means
electrons are being deflected which also depends on their mass and charge. Magnetic fields deflect lightest electrons. Cations are deflected based on their mass and weight.
Deposition
gas to solid
space
have energy, but no matter
Metalloids
low density, alright conductors
Properties of metals
shiny, malleable, good heat and electrical conductors, solid; high density, melting point, and boiling point
