Quantative Chemistry(3) Flashcards
What is the law of conservation of mass?
The law of conservation of mass states that no atoms are lost or made during a chemical reaction so the mass of the products equals the mass of the reactants.
Define relative atomic mass and relative
Average mass of atoms in an element taking into account masses and abundance of its isotopes, relative to 12C.
Define relative formula mass
Sum of relative Atomic Mass of all atoms in the formula.
What is Avogadro’s constant?
The number of atoms, molecules or ions in a mole of a given substance. The value of the constant is 6.02 x 10 power of 23
What is the formula that links mass, molecular mass and moles together
Mass = Mr x Moles
State what we mean by a limiting reactant in a
chemical reaction
In a chemical reaction involving two reactants, it is common to use an excess of one of the reactants to ensure that all of the other reactant is used. The reactant that is completely used up is called the limiting reactant because it limits the amount of products.
Write down the two formulae that link concentration, mass/nr moles and volume together.
Concentration (g per dm3(cubed) = Mass (g)/Volume (dm3(cubed)
Concentration (mol per dm3(cubed) = nr of moles/volume (dm3(cubed)
What is the molar volume of a gas at room temperature and pressure?
1 mole of a gas at room temperature and pressure occupies 24 dm3
What is titration?
A technique for finding the concentration of a solution by reacting a known volume of this solution with a solution of known concentration.
How do you conduct a titration?
Step 1
Step 1
Rinse the pipette with a solution of unknown concentration. Use the pipette to measure out the known volume of this solution.
How do you conduct a titration?
Step 2
Step 2
Add an indicator (a substance that changes colour at the end of titration)
How do you conduct a titration?
Step 3
Rinse the burette
Use a burette to gradually
Step 3
Rinse the burette with a solution of known concentration. Discard the liquid.
Use a burette to gradually add the solution of a known concentration.Discard the liquid.
Use a burette to gradually add the solution of a known concentration.
How do you conduct a titration?
Step 4
When indicator changes colour
Step 4
When indicator changes colour (at the end point), the volume added is
recorded
How do you conduct a titration?
Step 5
Step 5
It is important to get concordant volume results - they have to lie close to each other
How do you conduct a titration?
Step 6
Step 6
Suitable calculations are performed to find the concentration.
Why is it not always possible to obtain the theoretical amount of product in a chemical reaction?
● The reaction may not go to completion because it is reversible.
● Some of the product may be lost when it is separated from the
reaction mixture.
● Some of the reactants may react in ways different to the expected
reaction (side reactions may occur).
How is the percentage yield of a product in a chemical reaction?
% Yield = Actual mass of a product
x100%
Maximum theoretical mass of product
What is atom economy?
A measure of the amount of starting materials that end up as useful products.
It is a ratio of the relative formula mass of desired product to the sum of relative formula masses of reactants.
What is atom economy?
A measure of the amount of starting materials that end up as useful products.
It is a ratio of the relative formula mass of desired product to the sum of relative formula masses of reactants.
What is the equation that has mass at the top (not in grams)—
Mass
Mole|relative formula mass
What is the formula that has number of particels at the top
number of particels particels
Moles X Avagadros constant 6.023 x10(to the power of 23)
What is the equation that has moles at the top
Moles
Conc in mol/dm3(cubed)|Volume in dm 3(cubed)
What equation has mass in grams at the top (not involving moles and Mr)
Mass (in g)
Conc in g/dm3(cubed)|Volume in dm3(cubed)
What does equation has voulme of gas at the top
Voulme of gas
Moles of gas|24dm 3
What equation has actual yield at the top
Actual yield
Pecentage yield| theoratical yield
What equation has rim of desired product at the top
Rim of desired product
Percentage atom economy| Relative formula mass of all reactants
What is relative atomic mass represented as
Ram or Ar
What is the relative atomic mass the average mass of
an element compared to carbon-12
What does the average mass take into account
The abundance of the naturally occurring isotopes
How can the relative formula mass be represented
By (rfm or Mr)
Write a balanced equation of magnesium reacting with hydrochloric acid.
What is the relative formula mass of:
The following reaction occurs in a test tube under a Bunsen Burner:
The carbon dioxide and water escape from the test tube. Use the equation to explain why.
They are both gases
Write down the two formulae that link concentration, mole/mass and volume together.
Involves moles
Write down the two formulae that link concentration, mole/mass and volume together.
Involves mass
What is dimming
It has lots of soot that blocks out the sun
