C3 Flashcards
(46 cards)
What are the formulae of these ions?
- Ammonium, ammonia, hydroxide, nitrate, carbonate, sulfate, silver
Ammonium - NH 4 (1+) Hydroxide - OH (1-) Nitrate - NO3 (1-) Carbonate - CO3 (2-) Sulfate - SO4 (2-)
What is the law of conservation of mass?
Atoms cannot be created or destroyed by a chemical reaction.
Reasons for mass increase in a chemical reaction?
If mass goes up, one of the reactants that is a gas may be oxygen (or any other gas), that gas will be counted in the reactants and increase the mass.
Reasons for mass decrease in a chemical reaction?
If the gas is open to the outside air/atmosphere, and not in a closed system, some products may leave as gases, reducing the mass.
Symbol equation and 2 half equations for sodium reacting with chlorine.
2Na(s) + Cl2(g) > 2NaCl(s)
Na > Na(1+) + e-
Cl2 + 2e- > Cl2(2-)
How do you write an ionic equation?
Break up the ions, aqueous’s, then cancel out the common things on each side of the equation. E.g.
CuSO4(aq) + 2NaOH(aq) → Na2SO4(aq) + Cu(OH)2(s)
Cu2+(aq) + 2OH–(aq) → Cu(OH)2(s)
What is a mole?
Amount of any substance that contains the same number of entities as there are atoms in 12.0g of carbon-12.
How many entities are there in one mole?
Avogadro constant. 6.022×10^23/mol.
How do you measure a mole of a substance.
Mass of 1 mol = its molar mass.
E.g. CO2 = 44g
Formula for finding mass of a substance using its mass and amount.
moles = mass/molar mass
What is the effect of a limiting reactant?
One reactant will be in excess, one will be limiting. The limiting reactant is used up and determines the amount of product formed.
Mole calculation method.
1) Balance the equation
2) Calculate RfM of what you want and RfM of the substance of which you know the mass.
3) See the ratio between the reactant and the product through their balancing numbers.
4) Use moles = mass/molar mass to find the desired mass.
How do you calculate stoichiometry (balancing numbers) of an equation?
1) Calculate the moles of each substance in the equation (moles = mass/molar mass)
2) Divide the moles in each substance by each of the lowest number of moles.
3) All the numbers will be whole numbers and those are the balancing numbers.
Define an endothermic reaction. Examples
An endothermic reaction takes in energy from the surroundings and is shown by a fall in temperature. Examples, neutralization and combustion.
Define an exothermic reaction.
An exothermic reaction gives out energy to the surroundings and is shown by a rise in temperature.
In an endothermic reaction, what will the reaction profile show?
The energy of reactants will be lower than the energy of the products. With the activation energy bump going higher then falling to the product level.
In an exothermic reaction, what will the reaction profile show?
The energy of the reactants will be higher than the energy of the products.
What is activation energy?
Minimum energy needed to start a reaction.
Define bond energy.
Energy needed to break one mol of a particular bond and is measures in kJ/mol.
Formula for bond energy calculations.
Energy change = energy required to break bond (usually on the left of the equation) - energy required to make.
What is a redox reaction in terms of oxygen?
A redox reaction is a reaction in which reduction and oxidation happens at the same time (of oxygen).
What is reduction of oxygen?
Loss of oxygen from a substance.
What is oxidation of oxygen?
Gain of oxygen by a substance.
What is the reducing agent (in terms of oxygen)?
The reducing agent is the substance that reduces the substance with oxygen (coincidentally the substance that is oxidised).
