A-level Chem Help please please please
Please I need incredible help with chemistry, specifically amount of substance, and I'd appreciate it a lot if people could give me websites with practice questions and videos with in depth summaries for topics in chem.
Genuinely I need an A* in Chem, which is killing me because right now I'm getting Ds. So. Please help.
Also, should I get tutoring?
Genuinely I need an A* in Chem, which is killing me because right now I'm getting Ds. So. Please help.
Also, should I get tutoring?
Original post by Devoid_Dusk
Please I need incredible help with chemistry, specifically amount of substance, and I'd appreciate it a lot if people could give me websites with practice questions and videos with in depth summaries for topics in chem.
Genuinely I need an A* in Chem, which is killing me because right now I'm getting Ds. So. Please help.
Also, should I get tutoring?
Genuinely I need an A* in Chem, which is killing me because right now I'm getting Ds. So. Please help.
Also, should I get tutoring?
i have this same problem. lmk if u do find anything.
thanksss
Original post by Devoid_Dusk
Please I need incredible help with chemistry, specifically amount of substance, and I'd appreciate it a lot if people could give me websites with practice questions and videos with in depth summaries for topics in chem.
Genuinely I need an A* in Chem, which is killing me because right now I'm getting Ds. So. Please help.
Also, should I get tutoring?
Genuinely I need an A* in Chem, which is killing me because right now I'm getting Ds. So. Please help.
Also, should I get tutoring?
Which exam board is this for?
For practice questions, StudyMind and Physics and Maths tutor are the best for all boards in my experience.
I personally would advise against getting tutoring until you have tried all the free options first - if and only if they don’t work. I’d also talk to your school about getting a tutor if you do decide you need one rather than asking for TSR to give recommendations / if any users here could tutor you.
https://studymind.co.uk/resources/
https://www.physicsandmathstutor.com/chemistry-revision/
Original post by TypicalNerd
Which exam board is this for?
For practice questions, StudyMind and Physics and Maths tutor are the best for all boards in my experience.
I personally would advise against getting tutoring until you have tried all the free options first - if and only if they don’t work. I’d also talk to your school about getting a tutor if you do decide you need one rather than asking for TSR to give recommendations / if any users here could tutor you.
https://studymind.co.uk/resources/
https://www.physicsandmathstutor.com/chemistry-revision/
For practice questions, StudyMind and Physics and Maths tutor are the best for all boards in my experience.
I personally would advise against getting tutoring until you have tried all the free options first - if and only if they don’t work. I’d also talk to your school about getting a tutor if you do decide you need one rather than asking for TSR to give recommendations / if any users here could tutor you.
https://studymind.co.uk/resources/
https://www.physicsandmathstutor.com/chemistry-revision/
AQA, and thanks for the advice and links
Original post by Devoid_Dusk
Please I need incredible help with chemistry, specifically amount of substance, and I'd appreciate it a lot if people could give me websites with practice questions and videos with in depth summaries for topics in chem.
Genuinely I need an A* in Chem, which is killing me because right now I'm getting Ds. So. Please help.
Also, should I get tutoring?
Genuinely I need an A* in Chem, which is killing me because right now I'm getting Ds. So. Please help.
Also, should I get tutoring?
Can you be more specific about what area(s) you need help with? Is it moles, empirical/ molecular formula, PV=nRT, ionic equations?
Original post by Devoid_Dusk
AQA, and thanks for the advice and links
https://www.thestudentroom.co.uk/showthread.php?t=7522364&p=99878600#post99878600
Have even more resources
Original post by Chem74
Can you be more specific about what area(s) you need help with? Is it moles, empirical/ molecular formula, PV=nRT, ionic equations?
Reacting masses, like water of crystallisation and limiting reactants
Original post by Devoid_Dusk
Reacting masses, like water of crystallisation and limiting reactants
These are very easy fixes. I would suggest you find some questions on these topics you’ve tried and got stuck on / have not understood and ask them here. I’m happy to walk you through them if that would help you.
Original post by Devoid_Dusk
Reacting masses, like water of crystallisation and limiting reactants
Limiting reactants
A reaction finishes when one of the reactants is all used up. The other reactant has nothing left to react with, so some of it is left over:
•
the reactant that is all used up is called the limiting reactant
•
the reactant that is left over is described as being in excess
Reacting mass calculations
The maximum mass of product formed in a reaction can be calculated using:
•
the balanced equation
•
the mass of the limiting reactant, and
•
the relative atomic mass (Ar) or relative formula mass (Mr) values of the limiting reactant and the product
12 g of magnesium reacts completely with excess hydrochloric acid to form magnesium chloride and hydrogen:
Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g)
Calculate the maximum mass of hydrogen that can be produced. (Ar of Mg = 24, Mr of H2 = 2)
Amount of magnesium =
= 0.5 mol
Looking at the equation, 1 mol of Mg forms 1 mol of H2, so 0.5 mol of Mg forms 0.5 mol of H2
mass of H2 = Mr × amount
= 2 × 0.5
= 1 g
Some examples 1 What mass of hydrogen is formed when 2 g of calcium reacts with hydrochloric acid?
Ca + 2 HCl → CaCl2 + H2
2 What mass of carbon dioxide is made when 22 g of propane is burned in oxygen?
C3H8 + 5 O2 → 3 CO2 + 4 H2O
3 What mass of iodine is produced when 7.1 g of chlorine reacts with potassium iodide?
Cl2+ 2 KI → 2 KCl + I2
4 What mass of aluminium oxide is produced when 135 g of aluminium is burned in oxygen?
4 Al + 3 O2 → 2 Al2O3
5 What mass of magnesium oxide is formed when 6 g of magnesium reacts with oxygen?
2 Mg + O2 → 2 MgO
6 What mass of carbon dioxide is formed when 2 kg of calcium carbonate reacts with hydrochloric acid?
CaCO3 + 2 HCl → CaCl2 + H2O + CO2
7 What mass of hydrogen is produced when 195 mg of potassium is added to water?
2 K + 2 H2O → 2 KOH + H2
8 What mass of oxygen is needed to react with 4.5 g of ethane (C2H6)?
2 C2H6 + 7 O2 → 4 CO2 + 6 H2O
9 What mass of oxygen is formed when 735 g of potassium chlorate decomposes?
2 KClO3 → 2 KCl + 3 O2
Original post by Chem74
Limiting reactants
A reaction finishes when one of the reactants is all used up. The other reactant has nothing left to react with, so some of it is left over:
The mass of product formed in a reaction depends upon the mass of the limiting reactant. This is because no more product can form when the limiting reactant is all used up.
Reacting mass calculations
The maximum mass of product formed in a reaction can be calculated using:
Example
12 g of magnesium reacts completely with excess hydrochloric acid to form magnesium chloride and hydrogen:
Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g)
Calculate the maximum mass of hydrogen that can be produced. (Ar of Mg = 24, Mr of H2 = 2)
Amount of magnesium =
= 0.5 mol
Looking at the equation, 1 mol of Mg forms 1 mol of H2, so 0.5 mol of Mg forms 0.5 mol of H2
mass of H2 = Mr × amount
= 2 × 0.5
= 1 g
Some examples 1 What mass of hydrogen is formed when 2 g of calcium reacts with hydrochloric acid?
Ca + 2 HCl → CaCl2 + H2
2 What mass of carbon dioxide is made when 22 g of propane is burned in oxygen?
C3H8 + 5 O2 → 3 CO2 + 4 H2O
3 What mass of iodine is produced when 7.1 g of chlorine reacts with potassium iodide?
Cl2+ 2 KI → 2 KCl + I2
4 What mass of aluminium oxide is produced when 135 g of aluminium is burned in oxygen?
4 Al + 3 O2 → 2 Al2O3
5 What mass of magnesium oxide is formed when 6 g of magnesium reacts with oxygen?
2 Mg + O2 → 2 MgO
6 What mass of carbon dioxide is formed when 2 kg of calcium carbonate reacts with hydrochloric acid?
CaCO3 + 2 HCl → CaCl2 + H2O + CO2
7 What mass of hydrogen is produced when 195 mg of potassium is added to water?
2 K + 2 H2O → 2 KOH + H2
8 What mass of oxygen is needed to react with 4.5 g of ethane (C2H6)?
2 C2H6 + 7 O2 → 4 CO2 + 6 H2O
9 What mass of oxygen is formed when 735 g of potassium chlorate decomposes?
2 KClO3 → 2 KCl + 3 O2
A reaction finishes when one of the reactants is all used up. The other reactant has nothing left to react with, so some of it is left over:
•
the reactant that is all used up is called the limiting reactant
•
the reactant that is left over is described as being in excess
Reacting mass calculations
The maximum mass of product formed in a reaction can be calculated using:
•
the balanced equation
•
the mass of the limiting reactant, and
•
the relative atomic mass (Ar) or relative formula mass (Mr) values of the limiting reactant and the product
12 g of magnesium reacts completely with excess hydrochloric acid to form magnesium chloride and hydrogen:
Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g)
Calculate the maximum mass of hydrogen that can be produced. (Ar of Mg = 24, Mr of H2 = 2)
Amount of magnesium =
= 0.5 mol
Looking at the equation, 1 mol of Mg forms 1 mol of H2, so 0.5 mol of Mg forms 0.5 mol of H2
mass of H2 = Mr × amount
= 2 × 0.5
= 1 g
Some examples 1 What mass of hydrogen is formed when 2 g of calcium reacts with hydrochloric acid?
Ca + 2 HCl → CaCl2 + H2
2 What mass of carbon dioxide is made when 22 g of propane is burned in oxygen?
C3H8 + 5 O2 → 3 CO2 + 4 H2O
3 What mass of iodine is produced when 7.1 g of chlorine reacts with potassium iodide?
Cl2+ 2 KI → 2 KCl + I2
4 What mass of aluminium oxide is produced when 135 g of aluminium is burned in oxygen?
4 Al + 3 O2 → 2 Al2O3
5 What mass of magnesium oxide is formed when 6 g of magnesium reacts with oxygen?
2 Mg + O2 → 2 MgO
6 What mass of carbon dioxide is formed when 2 kg of calcium carbonate reacts with hydrochloric acid?
CaCO3 + 2 HCl → CaCl2 + H2O + CO2
7 What mass of hydrogen is produced when 195 mg of potassium is added to water?
2 K + 2 H2O → 2 KOH + H2
8 What mass of oxygen is needed to react with 4.5 g of ethane (C2H6)?
2 C2H6 + 7 O2 → 4 CO2 + 6 H2O
9 What mass of oxygen is formed when 735 g of potassium chlorate decomposes?
2 KClO3 → 2 KCl + 3 O2
Water of crystallisation is basically just an empirical formula question, but instead of working our mass, then moles, then ratio of atoms, you work out mass, then moles then ratio of the anhydrous salt vs the water.
Water of crystallization questions
1. Glauber’s salt was a commonly used laxative. It is hydrated sodium sulfate.
mass of crucible and lid = 26.42 g
mass of crucible, lid and hydrated sodium sulfate= 30.55 g
mass crucible, lid and sodium sulfate after first heating = 28.26g
mass of crucible, lid and sodium sulfate after second heating = 28.24 g
Use these results to determine the formula of Glauber’s salt
M(Na2SO4) = 142.04 g mol1 M(H2O) = 18.0 g mol1
2. Stannous chloride is a very useful substance for testing for the presence of dissolved precious metals . It is hydrated tin chloride.
mass of crucible and lid = 19.26 g
mass of crucible, lid and hydrated tin chloride = 32.92 g
mass crucible, lid and hydrated tin chloride after first heating = 30.77 g
mass of crucible, lid and hydrated tin chloride after second heating = 30.74 g
Use these results to determine the formula of stannous chloride
M(SnCl2) = 189.60 g mol1 M(H2O) = 18.0 g mol1
Answers
1.
Glauber’s salt is Na2SO4 . 10H2O
2.
o stannous chloride is SnCl2 . 2H2O
Quick Reply
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