Worksheet-2
Name ________________________
TIME YOURSELF!!! THIS WORKSHEET SHOULD TAKE YOU MAX OF 1.5 HOURS !!!!!!!
1. A. The element cobalt (Co) has three radioactive isotopes used in medical studies. Atoms of
these isotopes have 30, 31, and 33 neutrons, respectively. Give the symbol for each of these
isotopes in the form of 𝑨𝒁𝑿
B. An atom of Zn contains 34 neutrons. What is its mass number and its isotopic symbol.
2. The element Lithium has an atomic weight of 6.94 u and has 2 isotopes. Calculate the
percentage abundance of lithium-6 and lithium-7 isotope based of the following information.
Lithium-6 = 6.0151 u
Lithium-7 = 7.0160 u
3. Complete the following table
35
Cl-1
27
Mass number
32
40
No. of protons
16
20
No of electrons
18
20
No. of neutrons
1
Al3+
27
30
10
28
14
40
4. A piece of pencil lead contains primarily carbon and weighs 500 micrograms. Determine the
number of carbon atoms present in the piece of carbon.
5. Which one weighs more: 5.00 grams or 0.0255 mol of CH3OH?
6. How many atoms of hydrogen atoms are contained in 2.00 g of ethyl ether C6H7N?
7. Butane (C4H10) undergoes combustion with pure oxygen gas.
Balanced Equation:
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a. How many grams of CO2 are produced when 88 grams of O2 are reacted with 450 grams of
butane?
8. C4H10 and C6H12 are both hydrocarbons. Which one contains higher mass percentage of
carbon?
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9. We react 280 grams of B2O3 with 100 grams of solid elemental Magnesium (Mg) to produce
magnesium oxide and elemental Boron (B)
Balanced reaction:
a. Calculate the theoretical yield for Boron and magnesium oxide.
b. The percentage yield of the reaction is 85%. Determine the actual yields of Boron and
Magnesium oxide.
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c. Determine how much (in grams) of the excess reagent will be left over after the reaction is
complete.
10. Suppose you isolate an organic acid from clover leaves and know that it contains only the
elements C, H and O. Combustion of 0.513 g of the acid in pure oxygen produces 0.501g of
CO2 gas and 0.103g of H2O. In a separate experiment the molecular mass of the acid was
determined to be 90.04 g/mol
a) Write a hypothetical chemical reaction to the best of your ability
b. Determine the empirical formula AND Molecular formula of the acid CxHyOz.
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