2017 A/L MCQ Review / CHEMISTRY

2017 A/L MCQ Review / CHEMISTRY (Part-1)

Question no

1. Atomic model proposed next to plum pudding model of J.J. Thompson was nuclear model. It was proposed by Rutherford. Therefore disproving plum pudding model was done by Rutherford.(1^st answer)

2.–Since all compounds contain more than 1 element, there should be polarizations in bonds because of electronegativity difference between atoms involved in bond. Therefore first choice is true.                                                                                                       –Shape of CO₂ is linear and that of BF₃ is trigonal planer, this proves that compounds are with different shapes. Therefore 2^nd choice is also true.                                                          Only BF₃ from given compounds do not obey octet rule (8 valence electrons in central atom after bond formation) as this is false this can be the answer.                                      BF₃ Is polar therefore, this can also be taken as an answer.                                                     Only XeF4 and BF₃ have lone pairs on central atom, therefore this statement is also true. (Answers will be 3 or 4)

3.This is an aldehyde (with CHO group). Therefore name end with suffix “al”. Only 3, 4 & 5 answers contain that suffix. Longest carbon chain in this compound include a triple bond therefore “yn” term should come before suffix. Only 5^th choice contain “yn” term. Note- “yne” term is not written in middle of a name. (Answer -5)

4.NH₂ OH is the answer. It contain 3 H. Each hydrogen is in +1 state (Total=+3) therefore N & O should collectively have -3, as no charge is on molecule. Since O is in -2 state, to make a total -3, oxidation state of N should be -1. (Answer-5)

Shapes originated from trigonal bi pyramidal shape is as follows. Bi pyramidal shape originate from 5 VSEPR pairs.  (Answer-2)