Moles, acids and pH Flashcards
(29 cards)
You are given 120g of calcium. How many moles of calcium have you been given?
use mass ÷ relative atomic mass = number of moles
30mol
A sample of rock contains 252g of iron. Calculate the number of moles of iron in the sample.
252 ÷ 56 = 4.5 mol
What is the formula for the number of moles of an element?
number of moles = mass ÷ Relative formula mass
What is the difference between relative atomic mass (Ar) and relative formula mass (Mr)?
Ar is the measure of the mass of one atom of an element.
Relative formula mass is the measure of the mass of one molecule of that compound.
Calculate the mass of calcium carbonate that would be needed to produce 224g of CaO.
400g
Calculate the mass of magnesium chloride that could be produced from 72g of magnesium. Assume that the chlorine is unlimited.
285g
Calculate the mass of calcium sulfate that could be produced from 80g of Ca. Assume that the sulfuric acid is unlimited.
272g
Calculate the mass of hydrogen peroxide that could produce 64g of oxygen.
2 H2O2 —-> 2 H2O + O2
136g
Calculate the mass of sodium sulfate that could be produced from 240g of sodium hydroxide.Assume the sulfuric acid is unlimited.
2 NaOH + H2SO4 —-> Na2SO4 + 2 H2O
How many moles of copper will be produced if we used 0.5mol of copper sulfate and 1mol of magnesium? Why? Calculate the mass of copper produced.
CuSO4 + Mg —> MgSO4 + Cu
0.5 mol of copper will be produced as copper sulfate is the limiting reactant.
= 31.75g
If one reactant is limiting, the other must be ____________.
in excess.
What are covalent bonds?
Non-metal and a non-metal atoms bonded together.
What are metallic bonds?
A metal and a metal bonded together.
What are ionic bonds?
A metal and a non-metal bo ded together. They share pairs of electrons to comete their outer shells to become stable.
What is the law of conservation of mass?
The mass of the reactants must equal the mass of the products.
If the law of conservation of mass is true, then why does the mass seem to change during reactions?
Substances can enetr or leave the reaction mixture in a non-enclosed system, e.g. an open container. This allows other reactants into the reaction, increasing the mass, or alternatively allows oroducts out of the system, thus reducing the mass.
2.40g of magnesium is heated in air. It forms 4.00g of magnesium oxide. Calculate the mass of oxygen gained.
1.60g
What does an ionic equation show?
The ions present in a reaction mixture.
What does a half equation show?
It is a model for the change taht happens to one reactant within a reaction.
What is the Avogadro Constant?
6.02 x 10^23
It is the number of entities within one mol.
What experiment should be done to ascertain whether or not a solution is endothermic or exothermic?
- Measure the start temperature of a solution ina n insulated container.
- Add the other reactant and stir.
- Measure the end temperature.
- Calculate the temperature difference between the start and the end.
A polystyrene cup is a good container to use as plastic is an insulator.
What are the axes labelled on a reaction profile?
y axis - energy
x axis - progress of reaction.
Explain why a mixture of nitrogeb abd hydrogen needs heating for it to react.
A certain amount of activation energy required. Activation energy is the minimum amount of energy required for a reaction to take place, as it breaks the bonds in the reactants.
Define an acid.
A substance between 0 and 7 on the pH scale that releases H+ hydrogen ions when dissolved in water.
