Formulae, Equations And Amounts Of Substance Flashcards
What is Avagadro’s constant?
6.02 * 10^23
What is a mole?
-The amount of substance that contains the same number of atoms or particles as 12g of Carbon-12
-It’s used because atoms are so small, it is very difficult to count the number of them accurately, so scientists use the mole to quantify them
what is the molar mass?
-Molar mass is the atomic/formula/molecular mass
-The units are g/mol
Acid + base/alkali = ?
Acid + base/alkali -> Salt +water
Carbonates + acid = ?
Acid + Carbonate -> Salt + water + Carbon dioxide
Acid + metal = ?
Acid + metal -> hydrogen + salt
What are precipitation Calculations/reactions?
-Precipitation reactions are when we mix two solutions containing soluble ions and they form an insoluble compound
Dm ^3 Conversions
-dm^3 = m^3 1000
-cm^3 = m^31000000
How do you convert Celsius to Kelvin?
-You must add 273 ( ‘c + 273)
Assumptions of an ideal gas
-We assume that the gas molecules are tiny compared to the spaces between them
-We also assume that there are no forces acting between the gas molecules
-We assume that the gas molecules move randomly
-Lastly, we assume that when the gas molecules collide, the collisions are elastic,
-Ultimately, there isn’t an ideal gas, but the equation above works well for many gases
What is the Ideal gas equation?
-pV = nRT
-Pressure (Pa/kPa) * Volume (m^3) = moles (moles) * ideas gas constant (8.314 J/molK) * temperature (K)
What is the Molar volume of gas?
-One mole of gas approximately has the volume of 24dm^3 at room temperature and pressure
What is the equation linking amount of moles, the molar volume of gas and volume?
Amount of substance (mol) = Volume (dm^3)/24
What is the equation linking amount of substance, mass and molar mass?
Amount of substance (mol) = mass(g)/Molar mass (g/mol)
What is the empirical formula?
-The molecular formula tells us the elements in a molecule and the number of atoms of each element; e.g. methane = CH4
-The empirical formula tells us the simplest whole-number ratio of the atoms of each element in a compound
-To work out empirical formula, we first list the mass of each elements , Then figure the moles by dividing by Ar
-Next we divide by the smallest number of moles given in ratio
-And then we round up or down, giving the ratio of 1:2
-Now we write this ration into the empirical formula, which gives us CH2
-In the case of decimals, we must multiply until all the digits are whole numbers
What is Atom economy?
-The atom economy tell us what percentage of the mass of the reactant atoms end up in the product we want
-The equation for this is as follows:
Atom economy = (molecular mass of desired product / sum of molecular masses of all the reactants) *100
-reactions with a high atom economy are more sustainable than reactions with a low atom economy because less of the mass reactants end up in waste products
-Other factors need to be considered too, such as energy use. For example, a reaction with high atom economy but requires high energy may be less sustainable
-Also the waste product may be used by a chemical producer as the starting material for a different reaction, increasing overall sustainability
What is Percentage yield?
-In a reaction it is very unlikely than well get 100% yield for numerous reasons
-for example, not all the reactant may react, sometimes side reactions take place making different products and sometimes some of our product may be lost in e.g filtration
-The equation for percentage yield is as follows:
Yield(%) = (Yield (mass provided) / Maximum theoretical yield (found using reacting mass calculation)) *100
-The yield and maximum theoretical yield can both be in grams or moles
-We can find the maximum theoretical yield via the reacting mass calculation
What is accuracy?
-Closeness of agreement of results
-Accurate results are close to the accepted value
What is error?
-Difference between individual measurements and accepted values
What is uncertainty?
-Range of Values within the measurement lies
What is concordant values?
-Values that agree with each other
-Within 0.1cm^3 of each other
How would i calculate error?
-Measuring equipment typically has uncertainty, or how sensitive it is to providing the accurate value - it is typically hard the smallest value on the scale
-The equation as follows is used to figure out uncertainty :
Error = Measured value - actual value
Error/actual value * 100 = % of error
How can I calculate uncertainty
-Uncertainty is the value given following a plus and minus sign, e.g, the uncertainty of a scale is +/- 0.005g
Uncertainty/value recorded *100 = % uncertainty
-The uncertainty value is doubled if a reading is taken twice, e.g in a change in value
Give the equation linking number of moles, mass and molar mass
Mass = Mr*mol
What is the equation to calculate concentration?
-Concentration = number of moles / Volume
-c (mol dm^3) = n (mol) / V (dm^3)
