Amount of substance Flashcards
What is Avogadro’s constant
6.02*10^23
What is a mole
The amount of substance
1 mole of any element equals the…
relative atomic mass in grams
What is molar mass
The mass in grams in each mole of the substance
What is the formula that relates moles, mass and mr
n=m/mr
What is molecular formula
The number of atoms of each element in a molecule
What is empirical formula
The simplest whole number ratio of atoms of each element in a compound
What is relative molecular mass
Compares the mass of a molecule with the mass of carbon 12
In hydrated salts the water of crystallization is shown in a formula with a…
large dot
What is the method for hydrated salts
1.Weigh an empty crucible
2.Add the hydrated salt into the weighted crucible
3.Weigh the crucible and the hydrated salt
4.Heat the crucible and contents gently for 1 minute
5.Leave the crucible to cool
6.Then weigh the crucible and anhydrous salt
What is concentration
The amount of solute in moles, dissolved in each 1dm^3 of a solution
What is the formula for concentration
C=n/v
What is standard solution
A solution of known concentration
What is molar gas volume
The volume per mole of gas molecules at a stated temperature and pressure
What is room temperature
293 kelvin(20 degrees)
What is room pressure
101Kpa
what is 1 mole of gas molecules at room temp and pressure
24dm^3
What is the formula for the amount in moles of a gas
n=volume/24
What is the ideal gas constant
8.31Jmol^-1K^-1
What is the ideal gas equation
Pv=nRT
p=pressure
v=volume
R=ideal gas constant
T=Temperature
What is the method to find the relative molecular mass
1.Add a sample of the volatile liquid to a small syringe
2.Weigh the small syringe
3.inject the sample into a gas syringe through the self-sealing rubber cap
4.Reweigh the small syringe to find the mass of the volatile liquid
5.Place the gas syringe in a boiling water bath
6.Record the pressure of the gas produced
What is Stoichiometry
The balancing numbers give the ratio of the amount(in moles) of each substance
Example:
2H2(g) + 02(g) –> 2H20(l)
2 mol 1 mol 2 mol
What is the method to identify an unknown metal
1.Weigh a sample of the metal and add to the flask
2.Using a measuring cylinder add 25cm^3 1mol dm^-3 HCL to the flask and quickly replace the bung
3.Measure the maximum volume of gas in the syringe
What is theoretical yield
The maximum possible amount of product
What is the formula for percentage yield
percentage yield=actual yield/theoretical yield*100
What is the limiting reactant
The reactant that is not in excess will be completely used up first
What is atom economy
A measure of how well atoms have been utilized
What is the formula for atom economy
atom economy=sum of molar masses of desired products/sum of molar masses of products * 100
