2.1.3 Amount of substance
No description yet. This curated deck is ready for daily study.
Card preview (11)
What is the formula for calculating the percentage by mass of an element in a compound?
% of an element = (number of atoms X relative atomic mass ÷ Mr) x 100
What is the equation for working out the number of atoms/ions/molecules in a substance?
Number of atoms/ions/molecules = Moles x 6.02x10²³
What is the method for calculating the empirical formula?
• Find the mass of both substances (usually given in the question) • Calculate the moles of both substances • Divide the mole values by the smallest value • Adjust the ratio. If the compound is out by 0.01, it can be rounded. If it isn’t, the compound must be scaled up. • Form the formula from the ratio
Non-required practical Describe the method for calcualting the amount of water in a hydrated salt.
• Find the mass of the anhydrous salt by taking away the mass of the crucible • Find the mass of water by taking away the hydrated crystals from the anhydrous • These 2 values are the masses which can be subsituted into the emprical formula method.
What is the equation for molar gas volume?
Moles (n) = volume (dm³) / 24 24,000 should be used if the volume is given in cm³
What is the ideal gas equation?
pV = nRT • P = Pressure (Pa) • V = volume (m³) • n = moles of gas (mol) • R = ideal gas constant (8.314Jmol⁻¹K⁻¹) • T = temprature (K)
How is Kelvin (K) converted into ℃?
+273
How is KPa converted into Pa?
Take the KPa value and add x10³ onto it
What is the equation for concentration?
Concentration = (moles X 1000) ÷ volume
What is the equation for % yield?
(Actual moles ÷ theoretical moles) x100
What is the equation for atom economy?
(Mr of desired products ÷ Mr of all products) x100