4.5.2 Chemical Quantities Flashcards
How many elements are there in the periodic table?
Over 100
What atoms are present in the compound H20.
This has 2 Hydrogen atoms and 1 oxygen atom
What atoms are present in the compound HNO3
This has 1 hydrogen atom, 1 nitrogen atom and 3 oxygen atoms
What atoms are present in the compound Mg(OH)2
This has 1 magnesium atom, 2 oxygen atoms and 2 hydrogen atoms as the two outside the bracket means you multiply everything inside the bracket by 2.
What do the symbols (s), (l) and (g) mean when they are written in an equation?
s = solid l = liquid g = gas
What does the symbol (aq) mean when it is written in an equation?
Aqueous - this means dissolved in water.
What is the conservation of mass law?
The law of conservation of mass states that
no atoms are lost or made during a chemical
reaction so the mass of the products equals the
mass of the reactants
H2+ Br2 -> HBr
Has the conservation of mass law been applied in this equation?
No, on the left there are 2 hydrogen atoms and 2 bromine atoms reacting. On the right there is only one hydrogen atom and one bromine atom - it looks like mass has disappeared.
What do we mean by reactant?
A substance which is reacting together with something else in a chemical reaction. They are found on the left of the arrow in an equation.
What do we mean by a product?
A substance which is produced or made in a chemical reaction. They are found on the right of the arrow in an equation.
Copper carbonate –> Copper oxide + carbon dioxide
In this reaction the mass of the test tube appears to go down. The conservation of mass law says this is not possible. Where has the mass gone?
Carbon dioxide is a gas so has left the test tube.
1g Magnesium is heated in the air. Afterwards it is weighed and has a mass of 1.2g. The conservation of mass law says that mass cannot just appear. Where has this mass come from?
The magnesium has reacted with oxygen atoms from the air
Magnesium + Oxygen –> Magnesium Oxide
Which element in the periodic table do we compare all other elements to when we find their mass?
Carbon 12
Use your periodic table to answer this question.
What is the relative formula mass of H20?
H2o = H + H + O
= 1 + 1 + 16 = 18
Use your periodic table to answer this question.
What is the relative formula mass of CaCO3?
CaCO3 = Ca + C + O + O + O
= 40 + 12 + 16 + 16 +16 = 100
Use your periodic table to answer this question.
What is the relative formula mass of Al(OH)3
Al(OH)3 = Al + O + O + O + H + H + H
= 27 + 16 + 16 + 16 + 1 + 1 + 1 = 78
Hydrogen + Oxygen -> Water
If I have 12.3g of Hydrogen and 8g of oxygen - how much water must I make?
20.3g as all mass is conserved
Hydrogen + Nitrogen –> Ammonia
If I start with 8g of Hydrogen and make 16.5g of ammonia - how much nitrogen must I have reacted with?
8.5g as the mass of all the reactants has to equal the mass of the products
What is a mole?
It is a number we use to count the number of atoms present. 1 mole = 6.02 x10power23 atoms! or 602000000000000000000000 atoms!
This is called avagadros constant
What is the equation to calculate moles?
Moles = mass (in grams) divided by relative formula mass
How many moles are there in 9g of water H20?
moles = mass divided by relative formula mass
relative formula mass for water = 18 (using periodic table)
moles = 9 divided by 18 = 0.5 mol
What do we mean by limiting reagent?
It is the reacting chemical which is completely used up in the reaction
What do we mean by ‘in excess’?
There will be some of the reactant left over, not all of it will react in the reaction.
What is the equation for concentration of a solution?
Concentration = mass divided by volume (in dm3)
How do you convert cm3 into dm3?
1dm3 contains 1000cm3 of liquid.
25cm3 therefore is 0.025dm3
What is the concentration of a solution containing 12g of salt dissolved in 500cm3 of water?
Concentration = mass divided by volume (in dm3)
500cm3 = 0.5dm3
Concentration = 12/0.5 = 24 g/dm3
What is the name of a compound made of magnesium and oxygen?
Magnesium Oxide - you always list the metal first and then the non metal. The non metals name is changed to end in ‘-ide’.
What is the name of the compound made of bromine and sodium?
Sodium Bromide - you always list the metal first and then the non metal. The non metals name is changed to end in ‘-ide’.
What is the name of the compound made of copper sulphur and oxygen?
Copper Sulphate - you always list the metal first and then the non metal. If oxygen is also present the non metal name is changed to end in ‘-ate’.
What is the name of the compound made of nitrogen, oxygen and iron.
Iron Nitrate - you always list the metal first and then the non metal. If oxygen is also present the non metal name is changed to end in ‘-ate’.
