Question

1. which of the following substances is not a diatomic gas at room temperature? a. o₂. b. cl₂. c. f₂. d. br₂. 21. carbon(ii) oxide is a poisonous gas due to its ability to a. remove oxygen from blood. b. form stable compound with haemoglobin. c. destroy the red blood cells. d. attack haemoglobin of red blood cells. 22. alkenes are relatively more reactive than alkanes because a. alkenes are more stable than alkanes. b. the double bond in alkenes is susceptible to nucleophilic attack. c. the c - h bond in alkenes are more polar than in alkanes. d. there is a high electron density at the double bond in alkenes. 23. the element that has no electron in the p - orbital is a. helium. b. neon. c. nitrogen. d. carbon. 24. which of the following statements about group 7 elements is correct? they a. are monoatomic. b. have low electron affinity. c. are highly electronegative. d. are good reducing agents. 25. consider the reaction represented by the equation: 2h₂o₂(l) → 2h₂o(l) + o₂(g) the mass of h₂o₂ that would be required to produce 22.4 dm³ of oxygen at s.t.p is o = 16.0, h = 1.0, vm = 22.4 dm³ a. 16 g. b. 34 g. c. 32 g. d. 68 g. 26. which of the following metals can be extracted by electrolysis? a. gold b. copper c. iron d. sodium 27. polymerization of ethyne gives a. benzene. b. polyethene. c. cyclohexane. d. polystyrene.

Explanation:

• Question 20: Oxygen ($O_2$), chlorine ($Cl_2$), and fluorine ($F_2$) are diatomic gases at room - temperature. Bromine ($Br_2$) is a liquid at room - temperature.
• Question 21: Carbon(II) oxide (carbon monoxide) is poisonous because it forms a stable compound with haemoglobin, preventing the normal binding of oxygen to haemoglobin.
• Question 22: Alkenes are more reactive than alkanes due to the high electron density at the double bond, which makes them susceptible to electrophilic attack.
• Question 23: Helium has an electron configuration of $1s^2$, with no electrons in the $p$-orbital. Neon has electrons in $p$-orbitals ($1s^22s^22p^6$), nitrogen ($1s^22s^22p^3$) and carbon ($1s^22s^22p^2$) also have electrons in $p$-orbitals.
• Question 24: Group 7 elements (halogens) are highly electronegative. They are diatomic, have high electron affinity, and are good oxidizing agents.
• Question 25: From the equation $2H_2O_2

ightarrow2H_2O + O_2$, at s.t.p., 1 mole of any gas occupies $22.4\ dm^3$. 1 mole of $O_2$ is produced from 2 moles of $H_2O_2$. The molar mass of $H_2O_2$ is $2\times1.0 + 2\times16.0=34\ g/mol$. For 1 mole of $O_2$ (22.4 $dm^3$ at s.t.p.), 2 moles of $H_2O_2$ are needed, and the mass of 2 moles of $H_2O_2$ is $2\times34 = 68\ g$.

• Question 26: Sodium is a highly reactive metal and is extracted by electrolysis. Gold, copper, and iron are less reactive and can be extracted by other methods such as reduction.
• Question 27: The polymerization of ethyne gives benzene through a cyclic trimerization reaction.

Answer:

• 20. D. $Br_2$
• 21. B. form stable compound with haemoglobin.
• 22. D. there is a high electron density at the double bond in alkenes.
• 23. A. helium.
• 24. C. are highly electronegative.
• 25. D. 68 g.
• 26. D. Sodium
• 27. A. benzene.