Measuring Matter
What is the numerical value of Avogadro's number?
6.02x10^23
What is the mass in grams of one mole of any pure substance?
Molar Mass
CuSO4.5H2O
Copper Sulfate Pentahydrate
What is the percent by mass of each element in a compound?
Percent Composition
What is a compound that has a specific number of water molecules bound to its atoms?
A Hydrate
What is the SI base unit used to measure the amount of a substance?
The mole
Why do one mole quantities of two different substances have different masses?
The substances have different compositions.
What is the C-Cl-F raito in CCl2F2?
1:2:2
What is the formula with the smallest whole-number mole ratio of the elements?
Empirical Formula
What happens when a hydrate is heated?
Water molecules are driven off leaving an anhydrous compound, or one "without water".
How many atoms of potassium does 1 mol of potassium contain?
6.02x10^23 potassium atoms
Explain how you would convert from number of atoms of a specific element to its mass.
Convert the number of atoms to moles, then multiply moles by the molar mass of the element.
5.50g compound x 1 mol compound/185.0g compound
0.0297 mol compound
What specifies the actual number of atoms of each element in one molecule or formula unit of the substance?
Molecular Formula
How can you determine the formula of a hydrate?
You must find the number of moles of water associated with 1 mol of the hydrate.
2.11x10^24 molecules sucrose x 1 mol/6.02x10^23 molecules sucrose
3.50 mol sucrose
Calculate the mass of 5.22 mol of He
20.9 g He
What information is provided by the formula for ptassium chromate (K2CrO4)?
One mole of K2CrO4 contains two moles of K^+ ions and one mole of CrO4^-2 ions.
Express the composition of sucrose (C12H22O11) as the mass percent of its elements.
144 g C
22 g H
176 g O
What three hydrates does Calcium Chloride form?
The recommended daily allowance of selenium in your diet is 8.87x10^-4 mol. How many atoms of selenium is this?
5.34x10^20 atoms Se
Convert to mass in grams.
4.22x10^15 atoms U
How many moles of oxygen atoms are contained in 2.50 mol of KMnO4?
10 mol O
1 mol Ni
1.936 mol C
2.031 mol N
What are some hydrates used for?
To store solar energy.