Topic 2 - Atoms, Molecules, and Stoichiometry Flashcards
What is an atom mostly made of?
Empty space.
What does the proton (atomic) number tell you?
The number of protons and electrons in an atom.
What does the mass number tell you?
The number of protons and neutrons in the nucleus of an atom
What is Relative Atomic Mass?
The weighted mean mass of an atom of an element, compared to 1/12th of the mass of an atom of Carbon-12.
What is Relative Isotopic Mass?
The mass of an atom of an isotope compared to 1/12th of the mass of an atom of Carbon-12.
What is Relative Molecular Mass?
The mean mass of a molecule compared to 1/12th of the mass of an atom of Carbon-12.
What are the two types of reaction equations?
Word and symbol.
What are the two parts of an equation?
The reactants and the products.
What is normally written above or below the arrow in equations?
A catalyst or practical conditions.
What are ionic equations?
Equations that show the ions that are formed in solution and show which particles are reacting.
What substances normally form ions in solution?
Acids, bases, and salts.
What are spectator ions?
Ions that don’t get involved in the reaction and don’t change.
What are the four state symbols?
(s) - Solid
(g) - Gas
(l) - Liquid
(aq) - Aqueous
What is a displacement reaction?
When a more reactive element takes the place of a less reactive element in a compound.
What do acids and bases form?
Salt and water.
What do carbonates also form in acids and bases reactions?
Carbon dioxide.
What is a precipitation reaction?
When a solid is formed is produced after 2 aqueous reactants react.
What are the three cations you need to know?
NH4^+ - Ammonium
Zn^2+ - Zinc (II)
Ag^+ - Silver (I)
What are the six anions you need to know?
SO4^2- Sulphate
CO3^2- Carbonate
HCO3^- Hydrogencarbonate
OH- Hydroxide
NO3 ^- Nitrate
PO4^3- Phosphate
What is Avogadro’s number (L)?
6.02x10^23
What is the formula to calculate the number of particles in a substance?
no. of particles = Avogadro’s number x no. of moles
What is the formula to calculate the mass of a substance using Ar or Mr?
No. of moles = mass (grams) / Mr or Ar
How do you convert m to dm to cm?
Multiply by 10 for each jump.
When converting units, how do you change the number you multiply for each dimension?
Add a 0 for each dimension added.
e.g. dm - cm = x10
dm^2 - cm^2 = x 100
dm^3 - cm^3 = x 1000
What is the formula to calculate the number of moles of a substance in solution?
No. of moles = concentration x volume
What are the units for concentration?
moldm^-3
What are the units for volume?
dm^3
What is the empirical formula?
The simplest whole number ratio of elements in a compound.
What are the four steps to finding the empirical formula for a compound?
- Write out the elements involved.
- Write the percentages as masses.
- Divide these by Relative Atomic Mass to get number of moles.
- Divide all the numbers by the smallest number of moles.
How do you find the molecular formula from the empirical formula?
Mr of empirical formula / Mr of molecular formula = y
Multiply all the atoms in the empirical formula by y.
What are the 4 steps for finding the water of crystallisation?
- Write out the 2 molecules involved.
- Write the masses of each molecule.
- Divide these by Relative Molecular Mass to get number of moles.
- Divide all the numbers by the smallest number of moles.
What are the three steps to using equations to work out theoretical masses?
- Write out equation and balance it.
- Work out Mr/Ar of species involved. Write these as mass in g.
- Divide the reactant to find 1g and multiply it by the mass given in the question. Do the exact same to the other side to work out the theoretical mass produced.
What is the equation for finding the number of moles in a gas equation?
No. of moles = volume / molar gas volume
What is the molar gas volume?
The volume a mole of gas occupies measured in dm^3mol^-1
At standard room temperature and pressure, what is the molar gas volume for any gas?
24dm^3mol^-1
At standard temperature and pressure, what is the molar gas volume for any gas?
22.4dm^3mol^-1
What is standard room temperature and pressure?
293K, 101.3kPa
What is standard temperature and pressure?
273K, 101.3kPa
