National Chemistry

2004 Credit Almost the answers

 
 1. (a) What elements are in air?
Oxygen and nitrogen. So what which box contains something they react to form?
(b) What elements are in a hydrocarbon? Carbon and hydrogen. So what which boxes contains something each of them will react to form?

2. Write the molecular formula - -use page 6 for number of carbons May need to draw out to get number of hydrogens.
C4H8; C5H12; C4H10; C3H8; C2H6 C4H8;
(a) page 6. Melts before 25oC Make sure it does not boil before 25oC
(b) Definition - same molecular formula different structure (or name)
(c) Which family of hydrocarbons reacts with bromine? C=C double bond; double 'e'

3. (a) What were the different substances that reacted with acids?
Actually most of these are salts and do not react with the acid.
(b) Page 5 of data book You will have to attempt each pair. Magnesium with each of the other second names and so on. ie magnesium bromide (again), magnesium hydroxide, magnesium iodide, magnesium sulphate and magnesium chloride. Now for sodium ....
(c) Write the charge on the ions above each name. +2; and -1; +1 and -1; +1 and -1; +1 and -1; +1 and -2; +1 and -1
Notice B, C , D and F are the same so cannot be a correct answer

4. (a) Concentration is the only value changed.

  2 mole/l 1 mole/l
  A Zn B Mg
  D Zn C Zn
  F Mg E Mg

Notice that A and B cannot be correct as metal changes as well.
Now add the temperature
   2 mole/l 1 mole/l
  A Zn, 30 B Mg, 30
  D Zn, 20 C Zn, 20
  F Mg, 30 E Mg, 20

D and C are possible; so are F and B.
Now look at powder or lump.

(b) Match concentration, temperature. metal and particle size to fastest.
Page 7 identifies the most reactive metal - Mg.
High or low temperature for fast reaction?

5. (a) TWO answers When do ionic conduct? - must be two the same. ionic conduct when a solution or molten.
(b) Needs to be COVALENT and NETWORK. When do covalent conduct? Never

6. (a) Definition must be learned. Same atomic number different mass number
(b) Write out electron arrangement of argon (2.8.8)and for each of the six boxes. Some are ions and some are atoms. 2,8,8 (ion) ; 2,8 (ion) ; 2,8,8,1 ; 2,8,8,1 ; 2,8,8,2 ; 2,8,8 (ion)

7. Charge, mass and position of electron (around nucleus)
mass = p + n

8. Write list of the five carbohydrates (fructose, glucose, maltose, sucrose, starch) and match up what they have in common.
Then it is a true or false for each letter.
A. Do glucose molecules react together ? T/F
B. Starch is made from sucrose ? T/F
C. Sucrose is one of the three reducing sugars T/F
D. glucose and sucrose are a pair T/F
E. the last one dissolves easily V
F. sucrose (number 3) can be broken down V

9. Diagram tells which electrode is +ve and which -ve. Use the reactions given.
Treat statements as true or false.
A. +ve ions move to +ve electrode - opposites attract T/F
B. Ni used up at +ve electrode - Ni is the +ve electrode T/F
C. galvaniSINg T/F
D. oxidation at +ve electrode - Ni loses electrons T/F
E. electrons along wires - solutION T/F

part 2

10. (a) How many carbons on main part of monomer? 2 and a double bond
(b) Look at the elements present - C, N, H What would they burn in oxgen to give? Must be toxic.

11. (a) Need to learn this definition. make alloys because better.
(b) (i) How much of the coin is aluminium ? 5% of 5,74g
(ii) Use figure from part (i). If you do not have a figure just use 5.74g
Since grams then mass of 1 mole required. Al = 27.
mass in question divided by mass 1 mole

12.(a) What are the products of the reaction of acid and carbonate?
What could get out of the beaker ?
(b)Label the axes using the words in the table. Create scales using at least half the graph paper.
Plot and join the dots.
(c) What effect has doubling the concentration got on amount produced?
Have all of the reactants doubled ?
(d) You are told the chemical name of marble chips (calcium carbonate) earlier in the question. Salt from hydrochloric acid - chloride

13.(a) the diagram gives clues as to what to write about - overlapped negative electrons and positive nucleus.
(b) (i) The diagram tells you what the dots are. Draw nitrogen out showing only outer 5 electrons. Three hydrogens are required
(ii) You only know one shape. Formula is NH3. draw bonds between the atoms.

14. Write out the molecular formulae.
(a)(i) How many bond for each atom – you can count in the diagram. Each C must have four bonds, etc
(ii)Use the molecular formulae - CH4O and CH2O. Two hydrogens down
(b) Again look at the molecular formulae - CH4O and C2H4O2 - one carbon and one oxygen extra.

15. Read the information above and below the diagram.
(a) Mark on the wire. Which electrode loses the electrons? indicator turned blue so something must have happened here.
(b) Show usually means a test and its result.

16. (a) Definition should be known 'ELECTR'olysis and what happens?
(b) When metals are or are not doing something page 7 helps. Where is Al ? Near the top therefore it is quite reactive.
(c) Copy from the data book page 7. Make sure you are forming chlorine.
  ie ---> Cl2
(d) TWO marks. Again comparing metals page 7 helps. Compare Sn and Fe. Sn is less reactive.

17. (a) Write out the ions – page 4 helps. Ag+ and HCO32-
(b) (i) Copy out the equation and put working underneath.
need three 'S' on left hand side
  Ag2S + Al ---> Ag + Al2S3
  Ag2S
  Ag2S

(ii) Silver appears. Involves metals. Page 7
(c) Mass is mentioned so need mass of 1 mole.
  Al2S3 = (2 x Al) + (3 x S) for 1 mole.
  = (2 x 27) + (3 x 32) = 150for 1 mole.

How much aluminium is is the compound?

18. (a) Where has the ammonia gas gone!
(b)What is pH of ammonia? Above 7 (alkali) or below 7 (acid) ?
Is it called an acid ?

19. (a) Read off of the graph. Up from 15 and along from 0.007
(b) Draw a line on the graph along from 0.004 and take the reading on the gas line.

20. Write out molecular formulae - C4H6; C5H8; C6H10 -for each molecule.
(a) Definition should be known -
(b) Use molecular formulae to make this up. CnH.....
(c) Draw the bromine atoms onto the structure on the paper. How many to each double bond? Two per double bond.
(d) Definition should be known. New structure must have one C=C and formula must be C4H6. cannot be straight.

21.Titration. Circle figures from the diagram ie 0.20 mol/l and 20cm3
(a) Look at what is in the flask with the reactant.
(b)(i) The figures from the experiment are 21.2, 20.7 and 20.5. Ignore rough result.
If no answer guess 5 and use for next part of question
(ii) Calculation using answer from part (i) – so at least select a figure. What other figure has to do with the acid ? 0.20 mol/l
You now have two figures.
Calculate the third figure (answer) concentration = mol/litre
If no answer guess 5 and use for next part of question
(iii) The answer from (ii) is for the acid.
Use the equation to find the figure for the potassium hydroxide.
H2SO4 + 2KOH ----> K2SO4 + 2H2O
  1 mole with 2 moles

therefore double KOH needed.

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