C4-Quantitative Chemistry
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What is Mr?
Relative formula mass has the symbol, Mr. To calculate the Mr for a substance: work out how many atoms of each element there are in the chemical formula.
What is the equation for moles in terms of m and mr?
M/mr
Equation for moles interms of volume and concentration
Vol x conc =mol
What is concentration measured in?
Mol/dm^3
What is volume measured in
Dm^3
What is mass measured in
Grams
What is giga in metres
10^9
What is mega in metres
10^6
What is kilo in metres
10^3
What is deci in metres
10^-1
What is centi in metres
10^-2
What is milli in metres
10^-3
What is micro in metres
10^-6
What is nano in metres
10^-9
What is the effect of a limiting reactant on the amount of product made?
Mass is measured in kilograms (kg) or grams (g). of product formed in a reaction depends upon the mass of the limiting reactant. This is because no more product can form when the limiting reactant is all used up.
how do you identify the limiting reactant in a chemical reaction?
To find the limiting reactant, you need to determine the number of moles of each reactant that is present in the reaction. Then divide each number of moles by the coefficient of the compound (eg: 2H2O, divide by 2). The smaller one is the limiting reactant
What is theoretical yield?
Highest potential product formed in a reaction
What is the actual yield
Actual yield is the actual mass of product formed through inneficiency
What are reasons for inefficiency, causing a reduced product?
Not all limiting reactant is used up Product escaping the reaction vessel Physical loss of product during transfer Reactants may act in different ways to the expected reaction
How do you calculate percentage yield?
Actual/theoretical x100
What is atom economy?
The amount of useful product as a percentage of total product formed. A measure of the amount of starting materials that end up as useful products Reactant A + Reactant B = Product + Waste
How do you calculate atom economy?
(Formula Mass of desired product/ Formula Mass of total product including waste) x 100
Why can percentage yield never be above 100%?
The yield in a chemical reaction cannot exceed 100% because of the Law of Conservation of Mass, which states that matter is neither created nor destroyed. Therefore, the total mass of reactants must equal the total mass of products.
How can concentration of a solution be changed?
Often, a worker will need to change the concentration of a solution by changing the amount of solvent. Dilution is the addition of solvent, which decreases the concentration of the solute in the solution. Concentration is the removal of solvent, which increases the concentration of the solute in the solution