Round 1: Naturally occurring silver exists as two isotopes. From the table above, calculate the average atomic mass of silver.
107.9 u
5
Round 2: Rubidium ignites spontaneously when exposed to oxygen to form Rb2O. Rubidium exists as two isotopes: Rb-85 (84.91u) and Rb-87 (86.91u). If the average atomic mass of Rubidium is 85.47u, determine the percentage abundance of Rb-85.
72%
10
Round 3: A small pin contains 0.0178 mol of iron (Fe). How many atoms of iron are in the pin?
1.07 x 10^22 atoms
5
Round 4: A sample of pure acetic acid CH3COOH contains 1.40 x 10^23 carbon atoms. How many moles of acetic acid are in the sample?
0.116 mol
20
Round 5: Find the molar mass of K2Cr2O7 and Fe2(SO4)3.
K2Cr2O7 = 294.2 g/mol
Fe2(SO4)3 = 399.91 g/mol
5
Round 6: Which sample has the largest mass?
A) 5.00 mol of C
B) 1.50 mol of Cl2
C) 0.50 mol of C6H12O6
B) Cl2 has 106 g
10
Round 7: Sodium chloride (NaCl) can be used to melt snow. How many moles of sodium chloride are in a 10kg bag?
171.1 mol
5
Round 8: Vitamin B12 (C17H20N4O6) is called riboflavin. What is the mass, in grams, of a single molecule of riboflavin?
6.25 x 10^-22 g
20
Round 9: Find the percentage composition of a pure substance that contains 7.22g nickel, 2.53g phosphorus and 5.25g oxygen.
Ni = 48.1%
O = 35.0%
P = 16.9%
10
Round 10: Calculate the mass percent of nitrogen in Sr(NO3)2.
13.24%
10
Round 11: Indigo (C16H10N2O2) is the common name of the dye that gives blue jeans their characteristic colour. Calculate the mass of oxygen in 25.0 g of indigo.
3.05 g
20
Round 12: A compound consists of 17.6% hydrogen and 82.4% nitrogen. Determine the empirical formula of the compound.
NH3
10
Round 13: Compound X contains 69.9% carbon, 6.86% hydrogen, and 23.3% oxygen. Determine the empirical formula of Compound X.
C12H14O3
15
Round 14: Olive oil is used widely in cooking. Oleic acid, a component of olive oil, contains 76.54% carbon, 12.13% hydrogen and 11.33% oxygen by mass. What is the empirical formula of oleic acid?
C9H17O1
10
Round 15: Tartaric acid, also known as Cream of Tartar, is used in baking. Its empirical formula is C2H3O3. If 1.00mol of tartaric acid contains 3.61x1024 oxygen atoms, what is the molecular formula of tartaric acid?
C4H6O6
20
Round 16: A hydrate of zinc nitrate has the formula Zn(NO3)2*xH2O. If the mass of 1 mol of anhydrous zinc nitrate is 63.37% of the mass of 1 mol of hydrate, what is the value of x?
