IMAT 2016 Q51 [Bond Angles]

Which of the following molecules contain bond angles of 180° in their gaseous states?

(Atomic numbers: H = 1; Be = 4; C = 6; Cl = 17)

  1. BeCl_2
  2. C_2H_2
  3. CCl_4

A. 1 and 3 only
B. 1 and 2 only
C. 1 only
D. 2 and 3 only
E. 2 only

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In chemistry, the bond angle is the angle between two bonds that are connected to the same atom. In the gaseous state, molecules can move around and rotate, so the bond angles can vary. However, some molecules have a specific arrangement of atoms that results in bond angles of 180 degrees in their gaseous state.

To answer this question, we need to look at the structures of the molecules in the list and determine which ones have bond angles of 180 degrees in their gaseous state.

BeCl2 - This molecule is made up of one beryllium atom and two chlorine atoms. In its gaseous state, the beryllium atom is bonded to the two chlorine atoms, forming a linear shape with bond angles of 180 degrees. Therefore, this molecule has bond angles of 180 degrees in its gaseous state.

C2H2 - This molecule is made up of two carbon atoms and two hydrogen atoms. In its gaseous state, the carbon atoms are bonded to the hydrogen atoms, forming a linear shape with bond angles of 180 degrees. Therefore, this molecule has bond angles of 180 degrees in its gaseous state.

CCl4 - This molecule is made up of one carbon atom and four chlorine atoms. In its gaseous state, the carbon atom is bonded to the four chlorine atoms, forming a tetrahedral shape with bond angles of 109.5 degrees. Therefore, this molecule does not have bond angles of 180 degrees in its gaseous state.

Based on this information, the correct answer is option B: 1 and 2 only.

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