1.The grid below represents periodic table. Study it and answer the questions that follow. The letters do not represent the actual symbols of the elements.
| A | ||||||||
| B | G | H | E | C | ||||
| J | I | L | ||||||
| D | N | M |
(a) (I) Indicate on the grid the position of an element represented by letter N whose electronic configuration of a divalent cation is 2:8:8 . ( 1 mark )
(II) Name the bond formed between D and H react. Explain your answer.(2 marks )
Ionic/electrovalent
D is electropositive thus donates two electrons to electronegative H
(III) Write an equation for the reaction between B and water. ( 1 mark )
Chemical equation 2B (s) + 2H2O(l) -> 2BOH(aq) + H2 (g)
(IV) How do the atomic radii of I and L compare. Explain. (2 marks)
(V) In terms of structure and bonding explain why the oxide of G has lower melting point than oxide of L. (2 marks)
(b) Study the information given below and answer the questions that follow.
| Formula of compound N | NaCl | MgCl 2 | Al2Cl6 | SiCl4 | PCl3 | SCl2 |
| B.P(0C) | 1470 | 1420 | Sublimes | 60 | 75 | 60 |
| M.P(0C) | 800 | 710 | At 8000C | -70 | 90 | -80 |
( I)Why is the formula of aluminium chloride given as Al2Cl6 and not AlCl3 ? ( 1 mark )
(II) Give two chlorides that are liquid at room temperature. Give a reason for the answer. (2 marks )
(III) Give a reason why Al2Cl6 has a lower melting point than MgCl2 although both Al and Mg are metals. (1 mark )
(IV) Which of the chlorides would remain in liquid state for the highest temperature range explain why? (2 mark )
(Kakamega)
2. a) Study the information given below and answer the questions that follow.
| Element | Atomic radius (nm) | Ionic radius (nm) | Formula of oxide | Melting point of oxide (‘C) |
| P Q R S T | 0.364 0.830 0.592 0.381 0.762 | 0.421 0.711 0.485 0.446 0.676 | A2O BO2 E2O3 G2O5 JO | -119 837 1466 242 1054 |
(i) Which elements are non-metals? Give a reason. (2mks)
(ii) Explain why the melting point of the oxide of R is higher than that of the oxide of S. (2mks)
(iii) Give two elements that would react vigorously with each other. Explain your answer. (2mks)
b) Study the information in the table below and answer the questions that follow (The letters do not represent the actual symbols of the elements)
| Ionization Energy_kJ/Mole | |||
| Element | Electronic configuration | 1st ionization energy | 2nd ionization energy |
| A | 2.2 | 900 | 1800 |
| B | 2.8.2 | 736 | 1450 |
| C | 2.8.8.2 | 590 | 1150 |
(i) What chemical family do the elements A, B and C belong? (1mk)
(ii) What is meant by the term ionization energy? (1mk)
iii) The 2nd ionization energy is higher that the 1st ionization energy of each. Explain
(1mk)
(iv)When a piece of element C is placed in cold water, it sinks to the bottom and an effervescence of a colourless gas that burns explosively is produced. Use a simple diagram to illustrate how this gas can be collected during this experiment. (3mks)
3. The grid below represents part of the periodic table. The letters do not represent the actual symbols.
| A | ||||||||
| B | X | G | Z | E | V | |||
| J | I | L | T | |||||
| D | N | M |
a) Select the most reactive non-metal. (1mk)
b) Write the formula of the compound consisting of
I.D and Z only. (2mk)
II. X and Z
c) Select an element that can form an ion of change +2 (1mk)
d) Which element has the least ionization energy? Explain (2mks)
e) Suggest with reasons a likely pH value of an aqueous solution of the chlorine of:(3mks)
T.
B
X
f) To which chemical family do the following elements belong? (2mk)
J
V
g) An element K has relative atomic mass of 40.2.It has two isotopes of masses 39 and 42. Calculate the relative abundance of each isotope. (3mks)
4.The grid below shows part of the periodic table study it and answer the questions that follow. The letters do not represent the true symbols.
| A | ||||||||
| B | C | D | E | |||||
| F | G | |||||||
| H | ||||||||
\(a) Which element forms ions with charge of 2-. Explain (2mks)
(b) What is the nature of the oxide formed by C. (1mk)
(c) How does the reactivity of H compare with that of E. Explain? (2mks)
(d)Write down a balanced equation between B and Chlorine. (1mk)
(e) Explain how the atomic radii of F and G compare. (1mk)
(f) If the oxides of F and D are separately dissolved in water, state and explain the effects of their aqueous solutions on litmus. (3mks)
5. (a) The grid below show part of the periodic table.(The letter do not represent the actual symbols).Use it to answer the questions that follow.
| T | Q | |||||||
| S | R | K | ||||||
| A | J | Y | U | L | ||||
| W | M | B | ||||||
| C | N | |||||||
| P | ||||||||
(i)Select the most reactive non-metal. (1mk)
(ii)Select an element that forms a divalent cation. (1mk)
(iii)Element Z has atomic number 14.Show its position in the grid. (1mk)
(iv)How do the atomic radii of U and J compare? (2mks)
(v)How do electrical conductivity of A and Y compare? (2mks)
(vi)How does the boiling point of elements K, L and M vary? Explain (2mks
(b) The table below gives information on four elements by letters K, L, M and N. Study it and answer the questions that follow. The letters do not represent the actual symbols of the elements.
| Element | Electron arrangement | Atomic radius | Ionic radius |
| K | 2:8:2 | 0.136 | 0.065 |
| L | 2:8:7 | 0.099 | 0.181 |
| M | 2:8:8:1 | 0.203 | 0.133 |
| N | 2:8:8:2 | 0.174 | 0.099 |
(a) Which two elements have similar properties? Explain. (2mks)
(b) Which element is a non-metal? Explain. (1mk)
(c) Which one of the elements is the strongest reducing agent. (1mk)
6. The grid given below represents part of the periodic table study it and answer the questions that follow. (The letters do not represent the actual symbols of the elements.)
| A | ||||||||
| B | ||||||||
| C | D | E | ||||||
| F | ||||||||
(i) What name is given to the group of elements to which C and F belong? (1mk)
(ii) Which letter represents the element that is the least reactive? (1mk)
(iii) What type of bond is formed when B and E react? Explain (2mks)
(iv)Write formula of the compound formed where elements D and oxygen gas react. (1mk)
(v) On the grid indicate the a tick (√) the position of element G which is in the third period of the periodic table and forms G3- ions. (1mk)
(b) Study the information in the table below and answer the questions that follow. (The letter do not represents the actual symbols of the substance).
| Substance | Melting point oC | Boiling point oC | Solubility in water | Density at room. Temp/g/cm3 |
| H | -117 | 78.5 | Very soluble | 0.8 |
| J | -78 | -33 | Very soluble | 0.77x 1-3 |
| K | -23 | 77 | Insoluble | 1.6 |
| L | – 219 | -183 | Slightly Soluable | 1.33 x 10-3 |
I.(i) Which substance would dissolve in water and could be separated from the solution by fractional distillation. (1mk)
(ii) Which substances is a liquid at room temperature and when mixed with water two layers would be formed? (1mk)
II. Which letter represents a substance that is a gas at room temperature and which can be collected;
(i) Over water? (1mk)
(ii) By downward displacement of air? Density of air at room temperature = 1.29 x 10-3 g/C (1mk)
