Quantative Chemistry
- Created by: KHand21
- Created on: 27-02-17 17:15
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- Chemistry Calculations
- Formulae
- Balancing a formulae: count the amount of each element on both sides and change the numbers in front, until there are the same amounts.
- Word equations: which chemicals react together (reactants) and which chemicals are produced (products.)
- The formulae of a compound shows how many of each type of atom join together to make the compound.
- Empirical formulae: the formulae in it's simplest form.
- To convert to a molecular formulae, you do the Mr divided by the total mass in the empirical formulae.
- Symbol equation: shows the masses that will react or have been reacted.
- State symbols: (s) solid (l) liquid (g) gas (aq) aqueous
- Limiting reactants
- The chemical that will run out first
- The reactant in excess is still there at the end of the equation
- Balance the equation and the one will the lowest number of moles is the limiting reactant.
- The reactant in excess is still there at the end of the equation
- The chemical that will run out first
- Reacting masses
- 1. Balance the equation. 2. Write the given mass. 3. Write the Mr.
- Unknown mass = mass / Mr of known compound x Mr of unknown compound
- If you are given the mass of the reactant and product you can use ratios to answer the question.
- Mass is never lost or gained, it is conserved
- However some reactants may react in an unexpected way, some products may be lost and not all reversible reactions may be completed.
- 1. Balance the equation. 2. Write the given mass. 3. Write the Mr.
- Concentration
- The strength of a solution or how much solute is dissolved in the solvent.
- 1 L = 1 dm3 1ml = 1 cm3 1dm3 = 1000 cm3 or ml
- Molar concentration = moles of solute / dm3 of solvent
- % concentration = mass of solute / 100ml of solvent
- g/l concentration = mass of solute / dm3 of solvent
- The strength of a solution or how much solute is dissolved in the solvent.
- Mole calculations
- m = n / Mr n = m x Mr Mr = n / m
- 1. Balance the equation. 2. Mr calculations. 3. Find out the m or n. 4. Use the co-eff to work out the n or m of the product.
- Atom economy & percentage yield
- % yield = (actual mass / theoretical mass) x 100
- % is how much mass is lost.
- Atom economy = (Mr of desired product / sum of Mr of all reactants) x 100
- % of the product you want
- Percentage yields can be affected by: not scraping all of the product from equipment, having impureatives in the reaction and having side reactions.
- % yield = (actual mass / theoretical mass) x 100
- Formulae
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