Ch3 - Calcukatoons Flashcards
What’s the definition of an isotope
Same no of protons diff no of neutrons - with diff masses
How do we determine the mass number and abundance of isotopes?
Using a mass spectrometer
Definition of relative isotopic mass and relative atomic mass
The mass of an atom of an isotope compared with 1/12th the mass of carbon 12
The weighted mean mass of an atom compared with 1/12th the mass of carbon 12.
Definition of relative isotopic mass and relative atomic mass
The mass of an atom of an isotope compared with 1/12th the mass of carbon 12
The weighted mean mass of an atom compared with 1/12th the mass of carbon 12.
What are the charges of
hydrogen
Ammonium
Hydroxide
Carbonate
Nitrate
Sulfate
What are these ions called as a group
H+
Nh4+
Oh-
CO3 ^2-
NO3 -
SO4 ^2-
Polyatomic ions
When a non metal reacts with another element what does it end with
Ide
What’s the formula of zinc oxide
ZnO
Zn2+ O2-
It cancels out
What’s the formula of magnesium oxide
And calcium nitrate
Mg(OH)2
Mg2+ OH-
Need two ions to balance it out
Ca(NO3)2
Why is mass jumber decimal
Due to isotopes-have diff masses n RAM calc from averaging these diff isotopic masses
Can relative isotopic mass be a whole number
Does it have units
How many relative isotopic masses are there for each isotope
No always a whole number
No
One
What’s the empirical formula
What’s molecular formula
Tells us the simplest whole number ratio of the atoms of each element in a compound
Tells us the Elements in a molecule and the number of atoms of each element
Cyclohexane
Has 6 carbons and 12 H
What’s the empirical and molecular formula
C6H12
CH2
A compound contains 31.6% carbon
5.3% hydrogen and 63.1% oxygen
What’s the empirical formula
1) 31.6/12=2.63
2) 5.3/1=5.3
3) 63.1/16=3.94
1) 2.63/2.63=1
2)5.3/2.63=2
3)63.1/2.63=1.5
X it by 2 to make it a whole no ratio
C2H4O3
A compound contains 40% carbon
6.7% hydrogen
53.3% oxygen
Compound has a relative molecular mass of 180g/mol.
What’s the empirical and molecular formula
40/12=3.33
6.7/1=6.7
53.3/16=3.33
1
2
1
CH2O-30g/mol
180/30-6
Ch2O x6= c6H12O6
What’s the relative molecular mass
The weighted mean mass of a molecule compared with 1/12th the mass of an atom of carbon 12
How to calculate amount of substance(moles)
Mass/rfm
How to calc no of particles
Amount of substance x avogardos constant
A 50p coin has a mass of 8g and contains 75% copper by mass. Calculate the number of atoms of copper in a 50p coin. Rfm of Cu-63.5
0.75 x 8=6
6/63.5 =0.094
0.094 x 6 x 10 ^23
5.69 x 10^22
Calcukate the number of electrons in 98.9g of sodium
98.9/23=4.3 mol
4.3 x 6 x 10^23 = 2.59 x 10^24
11 electrons x 2.59 x 10^24
How to convert dm3- cm3
X 1000
what’s the stoichiometry of a reaction
the ratio of the amount in moles of each substance
what do chemists use balanced equations to find
the quantity of reactants required to prepare a required quantity of a product.
the quantities of products that should be formed from certain quantities of reactants.
How to calculate Concentration?
Conc(mol/dm3) = mol/ volume (dm3)
0.2 moles of potassium iodide was dissolved in water producing a final volume of 400cm3. Calculate the concentration
0.2/0.4
0.5 mol dm3
21.25g of sodium nitrate was dissolved in water. The final volume of the solution was 125cm3. Calculate concentration
21.25/ 85=0.25
0.25/0.125=2 mol dm3
How do u calcukate moles at rtp and pressure
Volume dm3/24
Calculate the volume of hydrogen gas produced when 13.08g of zinc is reacted with excess HCl- at rtp and pressure
Zn+ 2HCL——ZnCl^2+H2
13.08/65.4=0.2 moles
0.2 x 24= 4.8dm3
How to calculate volume of gas at any temperate and pressure
pV=nRT
Presssure(pa) x volume(m3)=moles x gas constant x temp(K)
How to convert from Kpa to pa
How to convert dm3-m3
How to convert from Celsius to K
How to convert from cm3-m3
X 1000
/ 1000
+273
/1000000
2.5 miles of hydrogen gas has a volume of 20dm3
Temp is 80 celcius
Calcukate pressure
Pv=nrt
2.5 x 353 x 8.314
—————
0.02
= 366855.25 Pa
4dm3 of oxygen reacted with unlimited sodium oxide. The reaction pressure was 200Kpa. Calcukate the mass of sodium oxide that’s reacted.
N=Pv/Rt
200000 x 0.0004
————————-
8.314 x 473
= 0.203 moles
0.203 x 2 ( there was a 2 in the acc equation)
0.406 x62=25.2g
0.267g of chemical evaporated to produce a volume of 97cm3. The temperature was 100 degrees and the pressure was 101000 Pa. Calcukate molar mass of chemical
97cm3/1000000=0.0000097cm3
N=pv/Rt
101000 x 0.000097
—————————
8.713 x 373K
=0.00316
0.267/0.00316 =84.5 gmol -1
What’s the atom economy and how do u calculate it
a measure of the amount of reactant that ends up as useful product
Molecular mass of desired product X100
————————————————-
Sun of molecular masses of all reactants
hydrogen is an important raw material and is produced from the reaction of carbon with steam. what’s its atom economy/
C + 2H20 (G)—–CO2 + 2H2
2h2=2 x 2=4
CO2=12+16 x 2=44
2x2/2x2+44 x 100 =8.3%
What do atoms with a high atom economy mean and how do u inc sustainablity
It’s more sustainable as less of the mass of reactants ends up in waste products
The waste product of one reaction can be used at the starying input for another reacyon
what is it and How to calculate percentage yield
the% ratio to the acc yield to the Theo yield
Yield/ max theoretical yield x 100
G or moles for units
CH4+ cl2—-CH3Cl+HCL
A scientist reacted 12g of methane with unlimited chlorine
The reaction Produced 15g of chloromethane
Calculate percentage yield of chloromethane
12/16=0.75 mol
0.75mol x 50.5g/mol
=37.88g (max theoretical yield)
15/37.88 x 100 = 39.6%
how to measure volume of gas with a gas syringe
fill a conical flask with 25 cm3 dilute HCL and then weigh a sample of the metal and add to the conical flask quickly and put the bung on top straight after and measure the max volume of gas in syringe.
how to measure volume of gas with a trough
fill a conical flask with 25 cm3 dilute HCL,then fill the 100ml measuring cylinder with water and invert this, placing the opening of the cylinder underneath the water in the trough. This can be secured in a vertical position with a retort stand.The delivery tube then be put inside the underwater opening of the cylinder.
A small piece of metal added to acid in flask, then close the bung, and start timing with stopwatch as soon as flask is closed.
wait 10 seconds and then read off the volume of gas in the inverted measuring cylinder each time 10 seconds passes. continue timing until the volume of gas does not change any more.
why is syringe worse than trough
it has a higher uncertainty and when the ,measuring cylinder is full at start of practical meniscus will fall on volume of gas produced at top of cylinder giving a more accurate volume than syringe
what could interrupt results based on this experiment
gas could be lost when removing bung to add sodium carbonate in
why is it better to measure the difference In mass
eliminates error from solid being left on the weighing boat
What’s are hydrated crystals
A crystalline structure containing water
What are anhydrous crystals
Crystalline form that contains no water
How does anhydrous copper Sulfate form
When blue crystals of hydrated copper Sulfate are heated the bonds holding the water within the Crystal are broken and water is driven off leaving behind anhydrous copper sulfate
What colour does powder go after water drives off
White but it’s very hard to get it fully white as it’s very hard to remove last traces of water by heat
What things could go wrong with this experiment if there wasn’t a colour change
All the water being lost- if hydrated and anhydrous form have diff colours we know surely when the waters driven off but we can only see the surface of the crystals and there may still be water inside and furthermore if there diff colours it’s definitley harder. To prevent this crystals are reheated until mass of residue no longer changed, showing all waters removed
No further decomposition-salts can decompose further when heated so if we heated the copper Sulfate even more it could turn black copper oxide if there was no colour change we could not of seen this
define avogadros constant
how to get conc in gdm3
the no of particles in 1 mole of a substance
(conc)mol dm3 x MM(g/mol)
equation for hydrated copper sulphate water of crystillisation
and what would happen in opposite direction
CuSO4*5H2O ⇌ CuSO4 + 5H2O
this hydrated to anyh opposite is vice versa
To calculate the percentage error, you take the error marked on the equipment, e.g. +/- 0.1ml, and divide this by whatever your measurement was, e.g. 25ml, then multiply all of this by 100 to get it as a percentage, so in this case, the percentage error would be 0.4%.
If you have taken more than one measurement, for example when calculating a change in temperature, then you multiply the error given (e.g. +/- 0.1 degrees), by the number of measurements that you have taken, and use the difference between them.
For example, you are measuring the temperature change of some water (maybe you’re calculating specific heat capacity or something), and the temperature rises from 18 degrees to 31 degrees. Your thermometer has marks for every degree, so its error is +/- 0.5 degrees. You have taken two measurements, so the error is doubled, to +/- 1.0. Your temperature change (31-18) is 13 degrees, so you calculate (1.0/13)x100 = 7.69%
Remember, the smaller the measurement you are taking, the larger the percentage error, so increasing sample size will reduce the error (as well as using equipment with a smaller error).
