Topic 3 Flashcards
What are the four states?
(g) gas, (l) liquid, (aq) aqueous, (s) solid
What is the arrow used for in chemical equations
To show reactants turning into products
What substances are always gases?
O2, N2, H2, Cl2 and any noble gases are always gases
What substances are always solids?
Metals
What substance is nearly always a liquid?
H2O (water)
What substances are aqueous most of the time?
Ionic compounds
What is the law of conservation of mass?
During chemical change there is no loss or gain of atoms. The mass of the products in a chemical reaction must equal the mass of the reactants
What 7 elements are diatomic molecules?
Oxygen, hydrogen, chlorine, nitrogen, fluorine, iodine and bromine
How to write and balance chemical equations?
- Write the correct formula for the reactants and products, including state symbols
- Count the number of each type of atom on each side of the equation
- If needed add coefficients in front of unbalanced substances until it’s balanced. Hint: balance oxygen and hydrogen last
What are ionic half equations for?
Used to show if electrons have been gained or lost (always add the electrons can’t subtract it and add them on the most positive side)
What is the relative atomic mass?
The average mass of the isotopes of an element compares to 1/12th the mass of an atom of carbon-12
How do you find relative atomic mass with abundance of isotopes?
atomic mass= (fractional abundance of isotope 1 x mass of isotope 1) + (fractional abundance of isotope 2 x mass of isotope 2)
What is the relative molecular mass?
The sum of all the relative atomic masses of each element in a compound. It has a unit of g mol-1
What’s the formula for moles using mass and molecular mass.
n=m/Mr
moles= mass/molecular mass
Why is volume used to find the number of moles of a gas?
Because the mass of a gas is so small. Equal amounts in moles of gases occupy the same volume under the same conditions
What is the molar gas volume?
The volume occupied by 1 mol of gas at room temperature and pressure (20 degrees and 1 atmosphere pressure) the standard value for this is 24dm^3
What is the formula for moles using volume and molar volume?
n=V/Vm or n=V/24
Moles= volume/molar volume
Moles= volume/24
What are the units for concentration?
mol/dm^3 and g/dm^3
What’s the formula for concentration?
concentration=moles/volume (c=n/V)
What’s the conversion from cm^3 to dm^3?
1000cm^3=1dm^3
How do you convert mol/dm^3 to g/dm^3
conc (g/dm^3) = Mr (g/mol) x conc (mol/dm^3)
What is a titration?
Titrations are used to accurately measure volumes and calculate concentration. Two solutions are used, one has a known concentration the other is unknown. They usually involve neutralization reactions: acid + base. The reaction is complete when the colour changes
What is the percentage composition formula?
Percentage composition = molar mass of element/molar mass of compound x 100
What is percentage yield?
The ratio of actual yield obtained compared to the expected or theoretical yield (in practice getting 100% yield is rare)
What is the formula for percentage yield?
percentage yield= actual yield/theoretical yield x 100
What is percentage purity?
The percentage of pure substance within an impure substance. Often the product you are trying to make may become contaminated with unwanted substances
What is the formula for percentage purity?
percentage purity= mass of pure substance/mass of impure substance x 100
What is Avogadro’s constant?
6.02x10^23 (the amount of atoms in one mole of a substance)
What is actual yield?
The recorded amount of product obtained
What is theoretical yield?
The amount of product that could be obtained under perfect conditions
What is the empirical formula?
The simplest whole number ratio of the different atoms or ions in a compound
What is the molecular formula?
The actual formula of a compound
What is a mole?
The number of particles which is equal to the number of atoms in 12g of carbon 12
