Write answers using complete sentences. Show work for all calculations!
The number under an atomic symbol in the periodic table has two meanings:
If you consider just one atom of that element, what does that number mean and what are the correct units for it?
If you consider a mole of atoms of that element, what does that number mean and what are the correct units for it?
Consider the list of units below. Write each unit in the box that corresponds to the category for that unit.
Common Units
g mL
g/mL mol
g/mol m
m2 sec
Used for Measuring Amounts of Materials
Characteristics of Materials which Can be Used as Conversions
Moles: Numbers and Masses
Molar Masses
For each of the following elements or compounds calculate the mass of 1
mole of particles of that substance. Express answers in units of
g/mol. Use at least five significant figures for the mass of each element when calculating molar masses.
CO2
Ba3(PO4)2
C6H12O6
AgNO3
Putting Molar Masses to Work
For each of the masses, convert to number of moles. For each quantity given in moles, convert to mass in grams. Express each answer with the correct number of significant figures.
5.9 mol CO2
3.8 × 10-3 mol Ba3(PO4)2
1.2 kg C6H12O6
37.98 g AgNO3
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Comparing Moles
Compare the following pairs of samples on the basis of the number of particles (the number of moles, not the mass). Which one has more particles? Circle the sample that has the larger number of particles.
116.89 g NaCl 117.56 g Ca(OH)2
49.542 g H2O 116.695 g BaSO4
Big Numbers
For each of the following amounts of materials, calculate the number of molecules given that [6.02 × 1023 molecules = 1 mol].
1.2 mol H2O
0.50 mol NH3
36 g H2O
8.5 g NH3
You have been given a container which weighs 49.87 g. You place a sample of glucose (C6H12O6) into it and weigh it and now it weighs 92.54 g. How many molecules of glucose are in the container?
Chloral hydrate (C2H3Cl3O2) is a drug formerly used as a sedative and hypnotic. It is the compound used to make “Mickey Finns” in detective stories.
Calculate the molar mass of chloral hydrate.
How many moles of C2H3Cl3O2 molecules are in 500.0 g of chloral hydrate?
What is the mass in grams of 2.0 × 10-2 mol chloral hydrate?
How many chlorine atoms are in 5.0 g of chloral hydrate?
What mass of chloral hydrate would contain 1.0 g Cl?
What is the mass of exactly 500 molecules of chloral hydrate?
Here is a chemical reaction: 1CO2 + 1H2O --> 1H2CO3
It says that one molecule of carbon dioxide (CO2) reacts with one molecule of water (H2O) to make one molecule of carbonic acid (H2CO3).
In reality, you cannot count the molecules because they are too small. Instead you must use mass. Using what you know about moles and molar mass find the mass of CO2 that would be required to react with 36.0 g of H2O to make 124 g of H2CO3.
Here is another chemical reaction: 2H2 + 1O2 --> 2H2O
It says that two moles of hydrogen (H2) react with one mole of oxygen (O2) to make two moles of water (H2O).
One mole of hydrogen has a mass of about 2 grams. One mole of oxygen has a mass of about 32 grams. And one mole of water has a mass of 18 grams. If you have 10 grams of hydrogen, how many grams of oxygen will react with it? Hint: convert to moles and consider that 1 mol of oxygen reacts with every 2 mol of hydrogen. Once you know how many moles, calculate the mass of oxygen using its molar mass.