Chapter 7 Flashcards
1 Mole = ?
6.022 x 10^23 items.
What is Avogadro’s number?
It is exactly 1 Mole (6.022 x 10^23)
1 mol of C9H8O8 = _ mol of C
9
Atomic mass of C = 12.01 amu
1 mole of C = __?
12.01 g
How do you find Molar mass of a compound ?
- Obtain the molar mass of each element
- Multiply each molar mass by the number of moles
- Calculate the molar mass by adding the masses of the elements
* *Round off the molar mass of an element to four significant figure for calculations**
Calculate the molar mass of vitamin D3, C27H44O.
384.6 g/mol
A salt shaker contains 73.7 g of NaCI. how many moles of NaCI are present?
1.26 mol of NaCI
What is the Empirical Formula?
The formula written with the lowest whole number ration of the atoms in a compound
What is the empirical formula for C4H8
CH2
How do you use Empirical Formula?
- Calculate the number of moles of each different element represented.
- Divide each of the number of moles by the smallest number of moles.
- (If #2 doesn’t give you whole numbers, you may need to multiply those numbers by 2, 3, 4, or 5 to get whole numbers.)
What is the Molecular Formula?
It shows the actual number of atoms of each element in a molecule. It is related to the empirical formula by a small integer such as 1, 2, 3.
Molecular formula = small integer x empirical formula.
What are the steps to solve Molecular Formula ?
- Determine the empirical formula
- Calculate the empirical formula mass in grams
- Calculate the small integer with the given molar mass
- Multiply the empirical formula by the small integer
Small integer = Molar mass of the compound / Empirical formula mass
Molecular formula = Small integer x empirical formula
What is the empirical formula of the compound if experimental analysis shows that a sample of the compound contains 6.87g of iron and 13.1 g of chlorine?
FeCI3
The empirical formula of ascorbic acid was C3H4O3-. The molar mass of ascorbic acid is 176.12g. Calculate the molecular formula of ascorbic acid.
C6H8O6
