4. Chemical Calculations Flashcards
You can work out the relative formula mass of a compound by…
adding up the relative atomic masses of the elements within it in the ratios shown by its formulae
One mole of any substance is…
it’s relative formula mass in grams
number of moles =
mass (g) / relative formula mass (Mr)
Balanced symbol equations tell you…
the number of moles of a substance involved in a chemical reaction
You can use balanced symbol equations to calculate the…
masses of reactants and products in a chemical reaction
You can figure out balanced symbol equations from the…
masses and the ratio of the number of moles of substances in a chemical reaction
The reactant that gets used up first is called the…
limiting reactant
The amount of a product produced in a chemical reaction is determined by…
the limiting reactant
What is the percentage yield of a chemical reaction?
How much of the product is actually made compared to how much could potentially be made
Some factors limiting the yield of a chemical reaction are…
-product being left behind in the apparatus
-reversible reactions not being completed
-some reactants producing unexpected and unwanted reactions
-losses in separating products from the reaction mixture
Why is it important to maximize atom economy in industrial processes?
To conserve Earth’s resources and to minimize pollution
The atom economy of a reaction…
uses its balanced equation to compare the relative formula mass of the product to the relative formula mass of the reactants, it is often expressed as a percentage
Concentration (g/dm³) =
amount of solute (g) / volume of solution (dm³)
A more concentrated solution has more solute in the same volume of solution than…
a less concentrated solution
Titration is used to…
measure accurately what volumes of acid and alkali react together completely
The point at which a reaction between an acid and alkali is complete is called…
the end point of the reaction
How can you show the end point of a reaction between an acid and alkali?
By using an acid/base indicator
You can use titrations to find the…
unknown concentration of a solution
You need to know the accurate concentration of one solution and then when the end point is established…
the balanced equation gives you the number of moles in a certain volume of solution
A certain volume of gas always contains…
the same number of gas molecules under the same conditions
What is the volume of 1 mole of any gas at room temperature and pressure?
24dm³ (24000cm³)
You can use the molar gas volume and balanced symbol equations to calculate…
volumes of gaseous reactants or products
