Name: ______Date: ______Period: ___
Mole Test Review 2012
¨ Mole
¨ Define mole using a word definition and mathematically
¨ Know who is responsible for defining the number of particles in a mole - Avogadro
¨ Molar Mass/Formula Mass
¨ What is molar mass?
¨ What is the unit for molar mass?
¨ Be able to calculate the molar mass of a compound, such as CO2 (44.009 g/mol)
¨ Percent Composition By Mass
¨ Know definition of percent composition
¨ Because percent means parts per100, the percents by mass of all the elements of a compound must always add up to 100.
¨ Formula for percent composition
Mass of element in one mol of compound x 100 = % by mass of the element
Molar mass of compound
¨ Conversions among mass, moles, and number of particles
¨ Know how to calculate moles, if given molar mass
¨ Know how to calculate molar mass, if given moles
¨ Do your conversion problems on the following pages!!
¨ Empirical Formula and molecular formula
¨ What is an empirical formula? … (reduced formula)
¨ What is a molecular formula? … (actual formula)
¨ The empirical formula may or may not be the same as the actual molecular formula. If the two formulas are different, the molecular formula will always be a simple multiple of the empirical formula.
¨ For calculating empirical formula from percent composition:
· Convert % directly to grams of the element (20.4 % = 20.4 g)
· Calculate moles of the element example: 20.4 g C x 1mol C = 1.698 mol C
12.011 g/mol C
· Calculate the simples ratio of moles of the elements by dividing each number of moles by the smallest value in the mol ratio
· Multiply the numbers of moles in the ratio by the smallest number that will produce a ratio of whole numbers
¨ Significant Figure ID
· All non-zero numbers are significant
· All “sandwiched” (captive) zeros are significant
· All leading zeros are NOT significant
· All trailing zeros are significant if there is a decimal in the number
· All trailing zeros before the decimal are NOT significant
¨ Significant Figure Calculations:
- or +, Use Least P.A.D from factors; / or x, use Least Sig Fi
2
A. Matching
2
1. Avogadro’s number_____
2. Molar mass_____
3. Mole_____
4. Percent Composition_____
5. Empirical Formula_____
a. The mass in one mole of any pure substance
b. Formula with smallest whole number ratio of elements
c. 6.02 x 1023
d. SI unit for amount of substance
e. Percent by mass of each element in a compound
2
4
B. Molar Mass calculations: Calculate the following molar masses. Show your work!
6. MgCl2 7. Cr(OH)2
8. C6H12O6 9. K2S
10. potassium sulfide 10. magnesium nitrate
4
C. Conversion problems: Perform the following conversions using dimensional analysis.
Report your answers with the appropriate significant digits.
10. In 25.5 g of Ag, determine the number of moles.
11. 1100 g of iron III oxide contains how many moles?
12. What is the mass of 3.25 moles of sulfuric acid (H2SO4)?
13. How many formula units of potassium hydroxide are in 2.55 grams?
14. Calculate the number of atoms in 22.6 grams of copper.
15. Calculate the percent by mass of each element in CaCl2.
16. Which has the larger percent by mass of sulfur, H2SO3 or H2S2O8?
17. A blue solid is found to contain 36.84% nitrogen and 63.16% oxygen. What is the empirical formula?
18. The chemical analysis of aspirin indicates that the molecule is 60.00% carbon, 4.44% hydrogen, and 35.56% oxygen. Determine the empirical formula for aspirin.
19. A sample of an ionic compound is analyzed and found to contain 60.2 g of silver and 10.6 g of fluorine. What is the simplest formula for this compound?
D. Multiple Choice:
20. What is the percent composition of oxygen in water?
a. 1g/mL b. 90% oxygen c. 88.809% oxygen d. 11.2% oxygen
21. What is the molar mass of Barium Phosphate?
a. 232.2g/mol b. 184.3g/mol c. 601.9 g/mol d. 559.6 g/mol
22. How many atoms are contained in a 3.0 mole sample aluminum?
a. 6.0 x 1023 b. 1.2 x 1024 c. 1.8 x 1024 d. 2.4 x 1024
23. What is the total number of nitrogen atoms in 0.25 moles of NO2 gas?
a. 1.5 x 1023 b. 6.0 x 1023 c. 3.0 x 1023 d. 1.2 x 1024
24. What is the empirical formula for a compound that contains 17.34% hydrogen and 82.66% carbon?
a. C5H b. C2H5 c. CH3 c. CH2
25. The molecular formula for succinic acid is C4H6O4. What is the empirical formula of the compound?
a. C4H6O4 b. C8H12O8 c. C2H3O2
26. A compound with an empirical formula of CH2 has a molecular mass of 70. What is the molecular formula?
a. CH2 b. C2H4 c. C4H8 d. C5H10
E. REVIEW CONCEPTS FOR NOMENCLATURE!!!!!
26. Write the formulas for …
a. lead (IV) sulfide ______
b. lead (IV) sulfite ______
c. lead (IV) sulfate ______
27. What are the formulas for …
a. iron (III) oxide ______b. iron (II) oxide ______
28. Write the formulas for …
a. sulfuric acid ______b. sulfurous acid______
29. Write the formulas for …
a. barium phosphate ______b. barium phosphite ______c. barium phosphide ______
30. What is the name of the following acid: HF? ______
31. Which Halogen has valence electrons in its 5th energy level? ______
32. Which Alkali metal has valence electrons in its 5th energy level? ______
33. How many valence electrons do the alkali earth metals have? ______
34. How many valence electrons are in Gallium? ______
35. Noble gases are inert, which mean they don’t react because they meet the octet. How many valence electrons are required to satisfy the octet? ______
36. Cations______electrons and have a ______charge. Usually they are ______.
37. Anions ______electrons and have a ______charge. Usually they are non______.
4