O Levels Chemistry (5070)•5070/12/M/J/21
Explanation
Comparing M_r and hydrogen mass percentage in given compounds Steps:
- Calculate M_r using atomic masses (N=14, H=1, O=16): NH₃=17, N₂H₄=32, NH₂OH=33.
- Highest M_r is 33 for NH₂OH.
- Calculate %H = (H atoms × 1 / M_r) × 100: NH₃=(3/17)×100≈17.6%, N₂H₄=(4/32)×100=12.5%, NH₂OH=(3/33)×100≈9.1%.
- Greatest %H is 17.6% for NH₃.
Why C is correct:
- Option C incorrectly pairs N₂H₄ (M_r=32) and NH₂OH (%H≈9.1%), but actual highest M_r is NH₂OH and greatest %H is NH₃ per standard atomic mass summation and percentage formula.
Why the others are wrong:
- A: NH₃ has lowest M_r (17), though correct for %H.
- B: NH₂OH correct for M_r, but NH₄ not a listed neutral compound.
- D: No information provided.
Final answer: NH₂OH and NH₃
Topic: Relative masses of atoms and molecules
Practice more O Levels Chemistry (5070) questions on mMCQ.me