# Chem Ch.3

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1. What is the basis of the atomic mass scale?
The Carbon-12 atom
2. What is the atomic weight of the C-12 atom?
Exactly 12 amu
3. What is used to determine the mass of individual atoms?
Mass Spectrometer
4. Since a F-19 atom is 1.583 times as heavy as a C-12 atom what is its atomic weight?
1.583 X 12.000 amu = 12 amu
5. What is the percentage of an atom's existence in nature called?
it's isotopic abundance
6. How do you calculate the average atomic mass of an element?
Multiply each isotope's atomic mass by it's (decimal) percent abundance and add them all together.

Ex: {Cl-35} 34.97 amu * .7553(75.53%) + {Cl-37} 36.97 amu * .2447(24.47%) = 35.46 amu
7. What is the equation for calculating average atomic mass?
(atomic mass Y1) * (% abundance Y1) + (atomic mass Y2) * (% abundance Y2)...= Average amu
8. The abundance of an isotope can also be found using...
the equation for finding the average atomic mass of the element
9. What equation can find the abundance of an element with 2 isotopes?
(A-Y1)/(Y2-Y1)
10. What represents the number of atoms of an element in a sample whose mass in grams is numerically equal to the atomic mass of the element?
11. If Sulfur has an atomic mass of 32.07 amu, then what is the mass in grams of a mole of Sulfur atoms?
32.07g
12. 1 mole = how many anything?
6.022*1023 Anything
6.022*1023
14. What is a molar mass equal to?
The sum of the atomic masses of the elements in a chemical formula
15. What is the sum of the atomic masses of the elements in a chemical formula equal to?
The molar mass of that chemical compound
16. What is the abbreviation for molar mass?
MM
17. What are the units for molar mass?
grams per mole (g/mol)
18. The mass percentage of an element in a compound is called the...
percent composition
19. Subscripts in chemical formulas represent atom ratios along with...
mole ratios
20. When given a compound's mass and the mass of its chemical components..finding the ratio between moles of each element gives you...
the compound's simplest chemical formula
21. If the percent compositions of the elements in a chemical compound are known, what can be found by turning those percentages into grams and calculating the mole ratios between the elements and converting to integers?
The simplest chemical formula
22. How do you find the simplest molecular formula when given the percent composition of the chemical compound.
Convert each percentage to grams out of 100, find amount of moles of each component, figure out ratios between each component, then find integers of each component that would be in the full compound.
23. How do you find the simplest chemical formula when given the amount of grams of a compound and the amount of grams of it's products after a reaction.
You would find the mass of each element in the original sample (using the simplest manners; ie subtracting for the more complicated one)..then find the # of moles of each element, then use the ratios to solve for the amount of each that was go into the compound.
24. Dividing the actual molar mass of a compound by the molar mass of its simplest formula, and multiplying that simplest formula by the ratio received gives you what?
The molecular formula of the compound
25. How do you find the molecular formula of a compound given the actual molar mass of the compound along with its simplest formula.
Find the molar mas of the simplest formula and divide the actual molar mass by it and use the ratio to multiply the simplest formula, which will give you the molecular formula.
26. Is the Molar mass of a compound or element equal to its atomic mass?
Yes
27. If the atomic mass of acetic acid is 60.0g/mol, what is its molar mass?
60.0 MM
28. When balancing equations, can you change subscripts within formulas?
No. Never...DON'T do it
29. The maximum amount of product you can possibly acheive from a reaction is called the...
Theoretical Yield
30. The reactant that suppresses a reaction from reaching it's full potential is called the...
limiting reactant
31. What is percent yield?
Experimental Yield over Theoretical Yield
 Author: ballinbc14 ID: 35303 Card Set: Chem Ch.3 Updated: 2010-09-21 06:34:13 Tags: chem mass relations stoichiometry Folders: Description: Mass Relations in Chemistry; Stoichiometry Show Answers: