Moles ✅ Flashcards
What is an isotope
Atoms that have the same number of protons but different number of neutrons, same atomic number, different mass number
Link equation with mass, moles, molar mass
Moles=mass/Mr
What is the empirical formula
Simplest whole number ratio of atoms of the elements in it
11.25g of hydrated cooper sulphate CuSO4.XH2O heated until it loses all of its water, new mass is 7.19g what is value of X
11.25-7.19= 4.06g of H2O
Moles of H2O=4.06/18=0.2255
Moles of CuSO4=7.19/159.6=0.0451
Ratio of CuSO4:H2O
1:5
X=5
What is the water of crystallization practical method
Weigh a crucible with its lit
Add between 1.3-1,5g of hydrated sulphate crystals, reweigh crucible
Place crucible containing hydrated sulphate on to a clay pipe triangle and gently heat for 2 minutes, take lid off periodically and carefully move crystals around with spatula whilst holding crucible with tongs
Allow contents to cool and re weigh crucible, it’s lid and contents
Continue to reheat and reweigh crucible lid and contents until mass is observed, allow to cool before reheating each time
What is the equation of moles of a gas
Volume (dm^3)=24Xmoles
What is the equation for density of a gas
Density (g cm^-3 or g dm^-3)= mass (g)/volume (cm^3 or dm^3)
Find volume of Hydrogen gas at room temp and pressure formed when 0.54g of calcium reacts with HCL
Ca+2HCl=CaCl2+H2
0.54/40.1=0.013467X24=0.323dm^3
A gas has a density of 3.4916g dm^-3, what is the Ar of a gas and what’s its identity
3.4916X24=83.718=Kr
What is the limiting reactant
In chemical reactions it is the substance that is used up first and stops the reaction
What mass of aluminum chloride is formed when 13.5g of aluminum reacts with 42.6g of chlorine
2Al+3Cl2=2AlCl3
Moles of Al=13.5/27=0.5
Moles of Cl2=42.6/71=0.06478
Al=2=0.5
Cl=3=0.6 so limiting reactant
So 0.6478moles of AlCl3/3 X2=0.4
0.4X133.5=53.4g
What is the equation for percentage yield
Percentage Yield = (Actual Yield/Theoretical Yield) x 100
What is the equation for atom economy
Atom economy=mass of wanted product from equation/total mass of products from equation
What is relative formula mass
Compares the mass of a formula unit with the mass of an atom of carbon-12, calculated by adding together the relative atomic masses of the elements in the empirical formula
What is the definition of water crystallisation
when some compounds can form crystals which have water within part of their structure
What is the equation for moles, concentration, volume of a solution
Moles=concentration (mol/dm^-3) X volume (dm^3)
What number is avogadro constant
6.02X10^23
What is relative formula mass
Compares the mass of of a formula unit with the mass of an atom of a carbon 12
Definition of concentration
the amount of a substance that is dissolved per unit volume of solution
What is theoretical yield
Maximum possible amount of product
What is atom economy
A measure of how well atoms have been utilized s
Why are reactions with high atom economy good
Produce a large proportion of desired products and few unwanted waste products
Are important for sustainability see they make the best use of natural resources
Definition of an acid
a substance which in an aqueous solution will release H+ ions.
Acids are also known as proton donors as they release a proton in the form of a H+ ion.
What is a weak acid
Eg Ethanoic acid (CH3COOH), only releases a small proportion of its available hydrogen atoms into solution as H+ions
A weak acid partially dissociates in aq solution
What is a strong acid
Eg HCL, releases all its hydrogen atoms into solution as H+ions and completely dissociates in aq solution
What is a base
A base neutralizes an acid to form a salt
What is an alkali
A base that dissolves in water releasing OH- into the solution
How to prepare a standard solution for titration
Solid is weighed accurately
Solid is dissolved in a beaker using less distilled water then will be needed to fill volumetric flask to the mark
Solution transferred to volumetric flask, rinsed with distilled water into flask
Flask filled to graduation line by adding distilled water until bottom of meniscus level
Volumetric flask inverted several times s
Describe the titration procedure
Add a measured volume of one solution to a convivial flask using a Pipette
Add other solution to a burette record reading let little bit out
Add few drops of indicator to conical flask and swirl
Run the solution of burette into conical flask and swirl until indicator changes colour record final burette reading= rough titration
Repeat 3 times, only calculate Concordant results
Work out unknown concentration of h2SO4
25cm^3 of 0.1moldm^3 KOH, mean titre= 25.7 of H2SO4
2KOH+H2SO4=K2SO4+2H2O
Moles of KOH= 0.1X0.025=0.0025
Ratio of KOH:H2SO4
2. : 1
0.0025:0.00125
0.00125/0.00257=0.0486moldm^-3
What is the ideal gas equation
PV=NrT
What are the 2 assumptions for the water of crystallization practical
All water has been lost
No further decomposition after heating
What is 1 dm3 equal to in Ml, L, Cm
1000ml
1L
1000cm3
What are the units for the ideal gas equation
Volume=m3
Pressure= Pa
Mol
Ideal gas constant= 8.31J mol-1 K-1
Temperature= K (273= 0 degrease)
