Quantitative Chemistry

1) What is the Conservation of Mass ?

2) What is Relative Atom Mass (RAM) ?
This can be read from the periodic table

3) What is Relative Formula Mass (RFM) ?

% mass of an element in a compound = (no of atoms of that element x relative formula mass of the compound) x 100

4) What is the formula for finding the number of moles in a given mass ?

5) What is the unit mol/dm(3) ?
moles per cubic decimetre) is the standard unit used in chemistry to measure molar concentration

6) When a substance is dissolved in a solution, can you describe the concentration ?
This is the amount of the substance (eg mass or no of moles) in a certain volume.

7) What is Titration ?
This is a precise laboratory technique used to find the exact concentration of an unknown solution by reacting it with a solution of known concentration.
This is a technique used to determine the unknown concentration of a specific chemical solution.

8) If the mass is not equal on both sides, what must have happened ?
Mass is always preserved so the relative formula mass on both sides must be equal.
The mass could have "Increased" if one of the reactants is a gas.
The mass could have "Decreased" if one of the products is a gas.

9) What does the large 2 represent in this chemical equation ?

Magnesium(s) + Hydrochloric Acid(aq) = ??(aq) + Hydrogen(g) 

The large 2 tells us there is 2 moles of that substance.

10) What is the concentration of a solution ?

Concentration(g/dm3) = Mass of Solute(g) / Volume of solvent(dm3) 

11) How can you convert mol/dm3 to g/dm3 ?

12) What is the atom economy ?

atom economy = ( relative formula mass of desired product / relative formula mass of all reactants ) x 100 

13) What does 100% atom economy mean ?
This means that all the atoms in the reactants have been turned into the desired product.
The higher the atom economy the greener the process.

14) Calculate the atom economy of the following reaction ?

Methane(g) + Water(g) = Carbon Monoxide(g) + Hydrogen(g) 

15) What is the percentage yield ?

percentage yield = (mass of product actually made / maximum theoretical mass of product) x 100 

16) What is the mass of one mole of the following elements and compounds ?
The RAM can be read from the periodic table

Carbon - RAM = 12, one mole = 12g 
Nitrogen - RAM = (2 x 14) = 18, one mole = 28g 
Carbon Dioxide - RAM = (12 + (2 x 16)) = 44, one mole = 44g 

Number of moles = ( mass in grams of the element or compound / relative atomic mass of the element or compound)

Questions

17) What is the symbol for the unit "moles"
mol

18) How many is one mole ?
6.02 x 10(23)

One mole contains this many particles (atoms, molecules, electrons)

The mass of one mole of any substance = relative atomic mass of the element or compound = relative formula mass of the element or compound.

19) How many moles are there in 66g of carbon dioxide ?

20) What is the mass of carbon if there are 4 moles of carbon dioxide ?

21) Calculate the relative formula mass for these compounds ?

Water(l) 

Lithium Hydroxide(s) 

Sulfuric Acid(aq)