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.

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?

2NaN3(s) --> 3N2(g) + 2Na(s) To inflate the air bag on the driver’s side of the car, 80.0g of N2 is required. What mass of NaN3 is needed to produce 80.0g of N2?

4C3H6(g) + 6NO(g) --> 4C3H3N(g) + 6H2O(g) + N2(g) What is the limiting reagent when 126 g of C3H6 reacts with 175g of NO?

Round 10: Calculate the mass percent of nitrogen in Sr(NO3)2.

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?

Round 9: Find the percentage composition of a pure substance that contains 7.22g nickel, 2.53g phosphorus and 5.25g oxygen.

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?

Round 1: Naturally occurring silver exists as two isotopes. From the table above, calculate the average atomic mass of silver.

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.

Round 3: A small pin contains 0.0178 mol of iron (Fe). How many atoms of iron are in the pin?

Round 7: Sodium chloride (NaCl) can be used to melt snow. How many moles of sodium chloride are in a 10kg bag?