3 - amount of substance Flashcards
How many atoms are in a mole|?
6.02X10^23. This is because 12 grams of carbon 12 contains 6.02X10^2 atoms.
What is an emperical formula?
The sinplest whole number ratio of atoms of each element in a compound
What is a hydrated salt?
When water molecules become part of the crystilline structure of a salt. This water is known as salt of crystilisation.
Give a method for finding the formula of a hydrated salt.
-Weigh an empty cruicible then add a hydrated salt to it and re weigh the cruicible.
-Support the cruicible on a pipe clay triangle on a triopod and heat gently for one minute then heat it strongly for a further three minutes.
-Reweigh the cruicible to find the mass of the anydrous salt.
ERRORS: all water is lost, salt doesnt further decompose.
What is the molar gas equation when at standard conditions?
moles = (Volume of gas cm3) / 24,000
What is the molar gas equation when conditions are not standard?
PV=nRT temperature must be in kelvin.
How do you convert from degrees centigrade to kelvin
+ 273
Stiochiometry definition
Theratio of the number of moles in different parts of the chmical equation
How would you determine the mass of an unknown metal using HCl
-Weigh a sample of the metal and add it to a flask with dilute hydrochloric acid and a gas syringe attatched. —–Measure the volume of gas collected and use stiochiometric equation to find moles of metal. You can then find Mr and identify unknown metal.
Why might you not acheive the theoretical yeild?
- Reaction may not have been completed.
- Other reactions may have taken place along side the main reaction.
- Purification of the product may result in loss of some product.
Equation for percentage yeild.
(Actual mass)/(Theoretical mass) X 100
What is atom economy? What is the equation?
The atom economy of a reaction is a measure of how well atoms have been utilised. (sum of molar masses)/(sum of molar masses of all products) X 100.
