2.1 atoms and reactions Flashcards
what is relative atomic mass
Weighted mean mass of an atom of an element compared to 1/12th the mass of an atom of carbon-12 which is taken to be exactly 12.
Has no units
Are a comparison between the element and carbon-12
Not a direct measure of mass of an atom.
Hydrogen- lightest so mass=1
Lithium is 7 time heavier so mass=7
Relative atomic mass= (isotopic mass * abundance)
100
what is relative isotopic mass
Mass of an atom of an isotope of the element compared to 1/12th of the mass of an atom of carbon-12
what is relative molecular mass
Weighted mean mass of a molecule of the compound compared to 1/12th of the mass of an atom of carbon-12
what is relative formula mass
Weighted mean mass of a formula unit compared to 1/12th of the mass of an atom of carbon-12
what is mass spec
The mass spectrum of an element shows a peak for each isotope of that element. The mass corresponding to each peak, together with their relative abundance can be used to calculate the relative atomic mass.
what does show mass spectra
The mass spectrum shows multiple peaks, the one with the largest m/z value, the molecular ion shows the relative molecular mass of that molecule.
The rest of the peaks show fragment ions formed when the molecule breaks up. Molecules break up more readily at weak bonds or bonds that give rise to fragments that are more stable.
Abundance against mass/charge
The peak number= number of isotopes.
what is the process that comes with mass spectrometry
The sample is bombarded with electrons (produces an ion).
The ion is accelerated by an electric field
The ion passes through a magnetic field to deflect.
Higher mass means less deflection.
A sensor detects and records the ions reaching it
what is meant by empirical formula
The simplestwhole number ratio of various atoms present in a compound.
Eg. The empirical formula of C2H6 is CH3
what is meant by molecular formula
Shows the exact number of different types of atoms present in a molecule of a compound.
what is moles
amount of substance that contains as many elemental particles as there are atoms in exactly 12g of12C
what is percentage yield
amount of reactant that is successfully converted into product is known as the yield.
% yield= actual yield X 100
theoretical yield
what is atom economy
Useful for industry as it shows waste product.
Can be improved by finding uses for the waste products, thus making it more sustainable
Mr of desired product X100
Mr of actual product
what is the laws that determine the ideal gas equation
Boyles law tells us volume is indirectly proportional to pressure. Higher pressure= lower volume
Charles’ law tells us volume is directly proportional to pressure. Higher temp= higher volume
Avogadro’s law tells us higher moles= higher volume
what are ideal gases
Molecules in random motion
No intermolecular forces present
Elasticcollisionswithno exchange of kinetic energy
Particles of 0 volume
how did the ideal gas equation get worked out
Real gases don’t follow these conditions exactly but do get close at high temperatures or low pressures.
All gas equations assume they do.
Volume of gas is directly linked toAvogadro’slaw, Charles’ law and Boyles’ law.
Combining these give either V∝n(T/P) orPV∝nT. By adding a constant of proportionality, which is known as the gas constant (R), you get the gas constant equation.
what is the ideal gas equation
Idea gas equation= P×V=n×R×T
n- moles, p- pressure, r- constant (8.413), V- volume, T- temp
Standard equations should use Pa and m3
1KPa= 1×103
1dm3= 1×10-3m3
Value of R is calculated at standard conditions to give
8.314 JMol-1K-1
what is dilution
Dilution = original concentration
Diluted concentration
Once the dilution has been calculated, the volume of the original stock that is required can be determined.
Remaining volume is given with distilled water.
Original stock volume= total volume needed
Dilution
what is standard solution
A standard solution is a solution with a known concentration.
how do you make a standard solution
- Dissolve the solute in a small amount of distilled water.
- If dissolved in a beaker, transfer to volumetric flask.
- Rinse the beaker with more distilled water and add to the flask to minimize residue left behind.
- Fill volumetric flask with distilled water till meniscus reaches the etch mark on the flasks neck.
- Ensure the etch mark is level with your eye.
what is concentration
The concentration of a solution is a measure of the amount of solute dissolved within a volume of solvent.
Moles = concentration × volume.
what is the difference between solvent and solute
Solute- substance that has been dissolved
Solvent- substance other chemicals dissolve in, usually water.
what are acids
Is a chemical that releases a hydrogen ion (H+), referred to as protons when dissolved in water.
Therefore is a proton donor and dissociates into it’s ions in water
what are the common acids
Hydrochloric acid- HCl Nitric acid- HNO3 Ethanoic acid- CH3COOH Sulfuric acid- H2SO4 Phosphoric acid- H2PO4
what are strong acids
Strong acids completely dissociates in water to release H+
At the same concentration, a stronger acid has a higher amount of protons released than a weak acid
what are weak acids
Weak acids partially dissociates in water to release some H+.
what are bases
Is a chemical that reacts with protons released by acids
Therefore is a proton acceptor
what are common bases
Metal oxides
Hydroxides
Alkali refer to soluble bases that release hydroxide ions (OH-) when they dissolve in water
what is ammonia
Is an alkali because when it dissociates it will react with water, generating ammonium ( NH4+).
what is salts
Acids react to form salts, an ionic compound formed when the H of an atom is replaced with a metal ion.
what is acid reactions
Acid + base → salt + water
Acid + alkali → salt + water
Acid + carbonate → salt + water + carbon dioxide
Acid + metal → salt + hydrogen
Ammonia forms ammonium ions so its salts are referred to as ammonium salts
what is water important for
Is an important for acid and alkali formation as H+ ions and OH- ions can only be formed in solution
what oxidation number
Shows the charge on an tom if all of its bonds are considered to be totally ionic.
what is the priority of oxidation states
Elements in their natural state = 0 Total oxidation states in a molecule= 0 Total oxidation state in an ion= charge Oxidation increases the x=oxidation state Reduction decreases the oxidation state
what is redox reactions
Involves the transfer of electrons, resulting in both oxidation and reduction of atoms.
what is disproportionation reactions
Where an element has been both oxidised and reduced
