Chapter 4 - Quantitative Chemistry 1 Flashcards
What element are all Atomic masses compared to ?
Carbon (C12)
What is the definition of RAM ?
The relative atomic mass of an element is weighted mean mass of the isotopes of an element compared with the C12 isotope, which has a mass of exactly 12
What is RFM ?
The relative formula mass is the sum of the relative atomic mass of all the atoms present the formula of a substance
What is the equation to find out the % of an element in a compound ?
mass of element in compound
= ———————————————— x 100
relative formula mass
What is a mole ?
the mass of one mole in grams is numerically equal to the relative formula mass or relative atomic mass
How do you calculate a mole ?
mass (g)
moles = ——————
RFM
How many grams in 4.5 tonnes ?
4,500,000 g
How many Kg in 56,000,000 mg ?
56 Kg
What is the equation to calculate percentage yield ?
actual yield
= ——————————– x 100
theoretical yield
What are the reasons why the percentage yield could be less than 100%
- some product may be lost when it’s separated from the reaction mixture
- side reactions may occur
- some reactions do not go to completion
What is the empirical formula ?
The empirical formula is the simplest whole number ratio of atoms of each element in a compound
What is the molecular formula ?
The molecular formula shows the actual number of atoms of each element present in a compound
How do you find the empirical formula from experimental data ?
-weigh a crucible a lid
-weigh a crucible a lid and the solid element
Place the crucible on a pipeclay triangle and heat, using tongs to raise the lid a little to allow air in for the solid to react.
- cool and weigh
-repeat the heating until the mass is constant
What is water of crystallisation ?
water of crystallisation is water that is chemically bonded into the crystal structure
What does hydrated mean ?
Hydrated means the crystal contains water of crystallisation.
