National Chemistry

2001 Credit    AMOST THE ANSWERS

 

 

part 1

 

1. (a) The only elements are Tin and Zinc

(b) The only elements are Tin and Zinc

Unlikely to be the same answer for both as they a doing different things to the   iron.

- page 7 shows what metals are above annd below iron in the  electrochemical series.

 

2.  (a) Write the concentrations beside each box letter to eliminate some more combinations

 

                                                    powder                           ribbon

    A                                 20oC   1 mol/l                     C   1 mol/l        40oC  

    B                                 20oC   1 mol/l                   F   1 mol/l        20oC

    D                                20oC    1 mol/l

    E                                20oC     2 mol/l

 

Must be F with A or B or D

 

Write in the name of the metal beside each box

 

                                               powder                           ribbon

    A                   Mg              20oC   1 mol/l                C   1 mol/l        40oC      Mg

    B                  Cu                20oC  1 mol/l             F   1 mol/l         20oC      Mg

    D                  Mg               20oC   1 mol/l

    E                   Fe               20oC   2 mol/l

 

 

Must be F with A or D

 

Now write in the name of the acids being used to eliminate the incorrect   combination.

 

(b)  If one of them does not react the experiment must be an odd one out  - You   could assume that magnesium is one that reacts reacts as it is in four  experiments.

 

3. (a) Mass number - number of protons = number of neutron

Number of protons = atomic number

Mass number and Atomic number are both given in each box

remember to pick 2 boxes

 

(b)  the same atomic number but different mass number = isotopes

If you are picking TWO isotopes then the boxes chosen must have something   in common.

remember to pick 2 boxes

 

(c) Electron arrangements are shown in page 1 of the data book

- find neon and write down its electronnic configuration = 2,8

- find each of the rest and write down  their electronic configuration

-  ions (boxes D and E) must have full  outer orbital of (usually) 8  electrons

remember to pick 2 boxes

 

4.  Obviously a different answer for each question - so getting the answer to any

  will eliminate an answer for another.

 

You could try naming any of the reactions to eliminate wrong answers.

 

A.   photosynthesis

B.  smaller molecule making larger molecule

C. breaking down large molecule to smaller molecule

D.  fermentation

E. breathing

 

(a) Yeast makes alcohol

(b) Hydrolysis occurs during digestion.

(c) A and B occur in plants

 

5. (a) hydroxides, carbonates and oxides neutralise acids.

remember to pick 2 boxes

 

(b) Use page 5 of data book - look each up separately - only one will form a   precipitate  ie be insoluble

 

6.  Find which boxes contain true statement for protons

centre of atom with a mass of one abed a positive charge

Find which boxes contain true statements for neutrons

centre of atom with a mass of 1 and a neutral charge

 

7.  "experiments(s)" in the credit paper usually means TWO correct answers.

X and Y will both need to be conductors

Conductors are

 molten ionic compounds, ionic solutions, metals and molten metals

Tick the conductors in column X

Tick the conductors in column Y

Hopefully there will be TWO experiments both with conductors

 

8.  In this style of question then there are TWO correct answers and three wrong   answers

- work through each statement individuaally deciding if it is True or False

see page 8 of the data book to identify transition metals

 

A.     find the colours associated with copper ions (blue ) and nitrate ions  (colourless) means copper nitrate is blue

B.     look at four of the coloured ions are Cu, Ni, Cr and Mn all transition metals ?

C      check that the four containing oxygen are all colourless MnO4 is purple

D.     check the three transition metals Cu2+, Ni2+ and  Zn2+ are coloured

E.      Li+ is colourless - will all lithium compounds be colourless ? What about Li+MnO4 - lithium (colourless) permanganate (purple)

 

9.  

In this style of question then there are TWO correct answers and three wrong   answers

- work through each statement individuaally deciding if it is True or   False.

 

A.   NH3 and CO2 are compounds

B.   Relative formula mass increases in the third column. Does critical  temperature also increase ? NO

C.  H2<and O2  are diatomic elements; He is monatomic (noble gases)

D.  Carbon dioxide becomes a liquid below its critical temperature of 31oC

 

part 2

 

10.  If bromine water is quickly decolourised then a C=C is present

(a) Can C5H12 be drawn out with a C=C ?       NO !   (view)

(b) Draw out hydrocarbon B remembering that it does not decolourise bromine water ie does not have a C=C

6 carbons = hex

(c) From the table what do C and D have in common ?  Both have same  molecular formula

of  C5H10but undergo different reactions so different  structural formulae.<

 

11.   (a) A metal reacts with H2O - what possible gases ? Not the metal or metal   compound; not chlorine it is not even there.  What gases could come from the water ?

 

(b) Easy to make hard to break

 

 Y to reacts with water  - this is a very reactive metal

W needed only heat to beak up the oxide -  an unreactive metal

 

(c) Only

 Y reacted with water - very reactive

Only

 W was obtained by heating alone - unreactive

X "kicked out" or displaced Z - X more reactive than Z

Most reactive first

 

(d) A metal oxide like Zn2O2-< produces Zn

                         e  Zn2+ ---->  Zn     try page 7 of data book

 

12.(a) Remember that you can only put figures in front of the formulae - you    CANNOT change any of the formula you have been given.

1 C on each side so that's okay

4 H on left so need 2H2O to get 4 H on right

(b) Try something bad like pollution or poison.

(c)  Underline the chemicals mentioned in the question ie sulphur S and hydrogen sulphide

 

                                                  H2S   ------->  S

Write under this the number of moles

                                    2 mole of H2S  ------->  3 mole of S

Write under this the mass of these moles

                                 2 mole  x 34g ------->3 mole x 32

                                           68 g ------->     96

                           

(d) (i) label both axes - copy the words from the box in the table

put on the scale  along the way each large box worth 10

up the way each large box worth 25;

make sure over half the graph paper is used;

plot points

make sure it is a line graph.

 

(ii) When making a statement about a relationship given in a graph you can   usually

frame your answer as follows "As the data along the way increases   then the data up the way increases or decreases (pick one)

Thus

As the temperature increases the solubility of sulphur dioxide ........(increases/ decreases - pick one)

 

13. (a) (i) ammonium ion and phosphate ion

(ii) For plants

(b) nitrate in this case - common acids are hydrochloric, nitric and sulphuric

(c) (i) Thermosetting thermo for "heat"  is "setting" unaffected by heat or softened by heat

(ii) How much N in CO(NH2)2< = 2 nitrogens present

then                     2 x N                                                                        x  100%

   mass of CO(NH2)   ie 1 C; 1 O; 2 N and 4 H

 

use masses on page 4 of data book

 

14.  (a)  31.5g is larger than 10.7; and 6.8 g is larger than 0.4 g

(b) Lots of ions pair a positive ion with a negative ion

(c) How many mole of calcium is 0.4 g ?

40 g = 1 mole of Ca

 

15.   (a) Electrons travel from metal higher up electrochemical series to metal ions  lower down.

Same occurs for non-metal species appearing in the electrochemical series on page 7

Find Br2 and  SO3 2-

(b) (i) At top of page 7 it tells electrochemical series shows reduction reactions

the first is Li+ e ----> Li  where Li gains an electron

Is the reaction in beaker B gaining or losing electrons ?

(ii)  H+ is appearing - what does this do to pH ?

(c) Beaker A has Br2 look for this on page 7.

Since Beaker B has electrons on the right hand side then beaker B needs electrons on the left hand side.

Copy out the one which has Br2 as a reactant.

 

16. (a) Haber and Ostwald process use catalysts that begin with the next letter in the alphabet.

(b) Ammonia is NH3 - notice that it asks for compounds

Very tempting to go for hydrogen and nitrogen but these are elements

What type of ion could possible give NH3 - try page 4  of data book

(c) negative electrons and positive protons?

 

17. (a) Alkanes is another example of a homologous series - what do alkanes have in common ?

(b) (i) X must contain something that is in the reactants ie C or H or Br or Na but not Cl - try counting.

6 C on both sides; 2 Br on both side etc.

(ii) each C makes 4 bonds; each H has one bond; each O has two bonds - just   draw

as written. Starting <CENTER>  <IMG SRC="2001chain.gif">

 

18.  (a) ion in solution producing solid

(b) Ca2+ and OH-

(c) carbon and oxygen seem to be missing from the right hand side

(d) Conducting electricity requires something to move.

 

19.  (a)  propyne C3<H4 and butyne C4H6

(b) (i) 3 C are still joined but now a triple bond bromines are missing; check hydrogens; circle anything missing on your question paper.

(ii) Look at the bromines

2001 Credit

          Hint area

          Almost the answers

           Answers.