Avogadro's Hypothesis
Relative Mass
What is Relative Mass?
- To determine a system of masses by comparison, one element would be chosen as the basis of comparison for all others.
Which element do chemists base the relative mass of all other elements on?
- Hydrogen
The Mole
What is a mole?
What is Avogadro's number?
What is Molar Mass?
How do you find the molar mass of an element? Of a compound? +examples
- A certain number of particles. The standard for measuring particles in chemistry.
What is Avogadro's number?
- 6.02 X 10^23
What is Molar Mass?
- The mass of 1 mol of a compound
How do you find the molar mass of an element? Of a compound? +examples
- To find the molar mass of an element, you look for it on the periodic table
- To find the molar mass of an element, you add together the molar masses of each element
Given the mass of an element, how could you determine the number of moles?
- You would set up a conversion from grams to moles
Given the amount of moles for a sample of a certain compound, how could you determine the mass of that sample compound?
- You would set up a conversion from moles to grams
Given the moles of a sample of a certain molecule, how could you determine the number of molecules in that sample?
- You would use Avogadro's number to convert moles to molecules
Given the mass of an element, how could you determine the number of atoms in that element?
- You would first convert grams to moles, then use Avogadro's number to convert moles to atoms
Percent Composition and Empirical & Molecular Formula
What is Percent Composition?
What is the difference between Empirical Formula and Molecular Formula?
How can % composition of a compound be used to determine the empirical formula?
Given the empirical formula and molar mass of a compound, how can you determine the molecular formula?
- The mass of each element in a compound compared to the entire mass of the compound, multiplied by 100.
What is the difference between Empirical Formula and Molecular Formula?
- Empirical Formula: The formula that gives the simplest whole number ratio of the atoms of the elements in a formula
- Molecular Formula: The formula that gives the actual number of atoms of each element in a molecular formula
How can % composition of a compound be used to determine the empirical formula?
- Using percent composition, you can determine the ratio at which particles combine. This ratio will determine how many molecules of each element combine in the empirical formula
Given the empirical formula and molar mass of a compound, how can you determine the molecular formula?
- Once you have obtained the empirical formula, must then determine its molar mass. You then divide the molar mass of the compound by the molar mass of the empirical formula
Chemical Structure Theory
What is Dalton's Theory?
- All matter is composed of indivisible particles called atoms
- All atoms of a given element are identical; atoms of different elements have different properties
- Chemical reactions involve the combination of atoms, not the destruction of atoms
- When elements react to form compounds, they react in defined, whole number ratios
How does the way in which chemicals combine/chemical structure impacts physical properties?
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