Calculations involving the mole
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what ion does silver (Ag) form?
Ag+
what ion does zinc form (Zn)?
Zn2+
what are isotopes?
atoms of the same element with different number of masses and neutrons but same proton number
what is the empirical formula?
the simplest whole number ratio of atoms of each element in a compound.
what is avagodros constant?
the number of particles of a substance in one mole of that substance. This has a value of 6.02 times 10 to the power of 23.
how do you calculate the amount of a substance (mol)?give units
mass(g)/ molar mass (g/mol) Mr
how do you calculate the number of atoms in a substance?
amount of substance(mol) times the Avogadro constant.
how do you convert from dm cubed to cm cubed?
times by 1000
what is the molecular formula?
the number of atoms of each element in a molecule
what is relative molecular mass?
the mass of a molecule compared with the mass of an atom of carbon-12.
how do you calculate concentration (mol/dm cubed)?give units
amount of a substance(mol)/volume(dm cubed)
what is the molar volume of any gas approximately?
24dm cubed
how do you calculate the amount of substance (mol) of a gas at room temperature and pressure?
volume (dm cubed)/24
what is the ideal gas equation?give units
pressure (Pa) multiplied by volume (m cubed) equals amount of substance(mol) multiplied by ideal gas constant multiplied by temperature (K)
how do you convert from cm cubed to m cubed?
divide by 1 million
how do you convert from degrees celsius to kelvin (K)?
add 273
for an ideal gas, what assumptions are made?
-the gas molecules are tiny compared to the space between them. -no forces acting between the gas molecules - gas molecules move randomly the Collins are elastic
when is the ideal gas equation used?
when the gases may not be at room temperature or pressure
how can you determine the volume from a liquid chemical?
1) measure the mass of an empty syringe and cap using a balance 2) remove the cap and draw a small volume of our chemical into the syringe. Replace the cap to seal the chemical. 3) reweigh the gas syringe containing the chemical and cap. 4) calculate the mass of the chemical by subtracting the initial by the other mass 5) boil the chemical so it turns from a liquid to a gas. Place the syringe in a beaker of boiling water 6) once boiled, read the volume of the gas on the scale of the gas syringe. You can use the volume to determine the molar mass of the chemical.
what is water of crystallisation?
crystals which contain water molecules apart of their crystalline structure which is called a hydrated compound. In a formula, it is shown by a dot.
in a formula, how can you tell how many water molecules are needed for a compound?
after the compound, a dot and the number of water molecules needed for that compound is shown.
what occurs when you heat hydrated compounds?
the bonds holding the water molecules in the crystal will be broken, creating steam. An anhydrous compound is left. Anhydrous means no water in the compound.
what does hydrated copper sulphate form?
blue crystals
what are the assumptions made from the experimental formula of hydrated copper(II) sulphate?
assumption 1- all water has been lost assumption 2-no further decomposition. Many salts decompose further when heated.