JAMB Physics 2023 Paper

Concept:Relative density compares the mass of a substance with the mass of an equal volume of water.Explanation:Mass of empty bottle is $m_b = 19\,g$.Mass of bottle filled with water is $66\,g$.Therefore, mass of water only is:$m_w = 66 - 19 = 47\,g$.The relative density of alcohol is $0.8$.The bottle holds the same volume each time, so:$RD = \frac{\text{mass of alcohol}}{\text{mass of equal volume of water}}$.Thus:$0.8 = \frac{m_a}{47}$.Mass of alcohol is:$m_a = 0.8 \times 47 = 37.6\,g$.Total mass when filled with alcohol:$m_b + m_a = 19 + 37.6 = 56.6\,g$.Answer:The mass of the bottle completely filled with alcohol is $56.6\,g$.