Supplemental Instruction
Iowa State University / Leader: / Tina Akinyi
Course: / Chem 177
Instructor: / Thomas Holme
Date: / 08/30/15
1. During the first week, a few terms and theories were introduced. To quickly review them, define the following:
-Matter
-Atom
-Law of conservation of mass
-Law of definite proportions
-Law of multiple proportions
2. Solve the following, paying attention to significant figures and decimal places:
a) (26.14/3.38) +4.2 b) 6.843 /(2.09-1.63)
3. Indicate how many significant figures there are in each of the following
a) 1.4270 b) 92, 500 c) 0.04107
4. Unit conversions
1 in=2.54 cm 0 F = (9/5) 0C + 320
Avogadro’s number = 6.022214179 * 1023 /mol
a) How many millimeters are present in 20.0 inches?
b) The volume of a wooden block is 6.30 in3. How many cubic centimeters is this?
c) How many atoms of hydrogen can be found in 45 g of ammonia, NH3?
d) Convert 78.8 0F to degrees Celsius
5. Isotopes, atomic weights and percent abundance
a) In a sample of 400 lithium atoms, it is found that 30 atoms are lithium-6 (6.015 g/mol) and 370 atoms are lithium-7 (7.016 g/mol). Calculate the average atomic mass of lithium.
b) A sample of element X contains 100 atoms with a mass of 12.00 and 10 atoms with a mass of 14.00. Calculate the average atomic mass (in amu) of element X.
c) Copper occurs naturally as Cu-63 and Cu-65. Which isotope is more abundant?
e) Silicon naturally occurs as three isotopes : Si-28 whose percent abundance is 92.23 %, Si-29 whose percent abundance is 4.67 % and Si-30 whose percent abundance is 3.10%. Calculate the average atomic mass of Silicon.
6. Fill in the table below (Hint: Use your periodic table and pay attention to atomic numbers and mass numbers)
Symbol / 27Al3+ / Kr / O2-Protons / 17
Neutrons / 48 / 8 / 18
Electrons / 18
Net Charge / 0