A glass beaker of unknown mass contains $74.0 \mathrm { ml }$ of water. The system absorbs $2000,0 \mathrm { cal }$ of heat and the temperature rises $20.0 ^ { \circ } \mathrm { C }$ as a result. What is the mass of the beaker? The specific heat of glass is 0.18 cal/g ∙ °C, and that of water is 1.0 cal/g ∙ C°.
A) 140 g
B) 560 g
C) 540 g
D) 270,000 g

Question

Quizplus · Accepted Answer

The heat absorbed by the water is:$$Q_w = m_w c_w \Delta T = (74.0 \mathrm { g })(1.00 \mathrm { cal/g \cdot ^\circ C })(20.0 ^\circ C ) = 1480 \mathrm { cal }$$The heat absorbed by the beaker is:$$Q_b = m_b c_b \Delta T = m_b (0.18 \mathrm { cal/g \cdot ^\circ C })(20.0 ^\circ C ) = 3.60 m_b \mathrm { cal }$$The total heat absorbed by the system is:$$Q = Q_w + Q_b = 1480 \mathrm { cal } + 3.60 m_b \mathrm { cal }$$Since the system absorbed 2000 cal of heat, we have:$$2000 \mathrm { cal } = 1480 \mathrm { cal } + 3.60 m_b \mathrm { cal }$$Solving for $m_b$, we get:$$m_b = \frac{2000 \mathrm { cal } - 1480 \mathrm { cal }}{3.60 \mathrm { cal/g }} = 140 \mathrm { g }$$Therefore, the mass of the beaker is 140 g.

A Glass Beaker of Unknown Mass Contains 74.0ml74.0 \mathrm { ml }74.0ml

A Glass Beaker of Unknown Mass Contains $74.0 \mathrm { ml }$