Waec Chemistry Past Questions For Year 2008

Question 6

Consider the following elements and their electronic configurations

W: 1s²2s²

X: 1s ²2s²2p⁶

Y: 1s²2s²2p⁶3s²

Z: 1s²2s²2p⁶3s²3p². Which of the elements belong to the same group in the periodic table?

waec 2008

• A. W and X only
• B. Y and Z only
• C. W and Y only
• D. W, Y and Z only

Question 7

Elements in the same group of the periodic table have

waec 2008

• A. the same number of valence electrons
• B. the same number of electron shells
• C. different chemical behaviour
• D. the same atomic size

Question 8

Which of the following statements is not true of halogens?

waec 2008

• A. they exist in different physical states
• B. they exist as diatomic molecules
• C. their ionic radii decrease down the group
• D. their melting and bolling points increase down the group

Question 9

Atom \(^{234} _{88} Q\) decay by alpha emission to give an atom R. The atomic number and mass number of atom R are respectively

waec 2008

• A. 86 and 230
• B. 87 and 234
• C. 88 and 233
• D. 90 and 238

Question 10

Which of the following compounds with the corresponding masses contain the highest percentage of nitrogen? [N = 14]

waec 2008

• A. NH₃ = 17
• B. NH₄CI = 53.5
• C. NH₄NO₃ = 80
• D. (NH₃)₂SO₄ = 132