Unit 3 - Quantitative chemistry Flashcards
(20 cards)
What happens to the total mass in a chemical reaction?
It is always conserved
What is relative formula mass?
The sum of all the relative atomic masses of atoms in a formula.
What is the relative atomic mass for CH4?
H = 1
C = 12
12 + (4 x 1) = 16
Why does the mass of the products sometimes seem less than the mass of the reactants?
If any gas is created as a product and leaves, mass may decrease
What is a mole?
A unit of measurement for the amount of a substance, which is 6.02 x 10^23.
What happens when a substance is dissolved in water?
It dissociates into its ions (e.g. H+ and Cl-) as does the water (into H+ and OH- ions)
What measurements can concentration be given in?
g/dm³ OR mol/dm³
What is the equation for concentration?
Moles/Volume (dm³)
How do we get from cm³ (ml) to dm³?
÷1000 e.g. 100cm³ = 0.1dm³
(EXAMPLE) What is the concentration of 7.3g if HCl is dissolved in 100cm³ of water?
-RAM of Hcl = 36.5
-Moles of HCl = 7.3 ÷ 36.5 = 0.2 mol
-Volume = 100 ÷ 1000 = 0.1dm³
-Concentration = 0.2 / 0.1
- = 2 mol/dm³
What is the equation for number of particles?
Moles x Avogadro’s constant
What is percentage yield?
The mass of product that is made in a reaction, compared to the maximum theoretical mass that could be made (USING ACTUAL MASS)
What is the equation for percentage yield?
Total mass of products/total mass of reactants, then x100 for percentage
(EXAMPLE) if 10g of ammonia is made from 20g of reactants, what is the % yield?
10/20 x 100 = 50%
What is atom economy?
Tells you how much of a desired product can be made in a reaction compared to the total mass of reactants (USING RELATIVE ATOMIC MASS)
What is the equation for atom economy?
RAM of desired product / total RAM of reactants, x100 for percentage
What volume does 1 mole of gas occupy? (at RTP)
24dm³
What is RTP and what are the properties?
Room temperature and pressure, 20 degrees C and 1 atmosphere
