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In an experiment, a piece of metal is heated to a high temperature and then placed in an insulated container with water. The initial temperature of the water is T_{i}=25^{\circ} \mathrm{C} and the initial temperature of the metal is T_{m}=150^{\circ} \mathrm{C}. After thermal equilibrium is reached, the final temperature of the water and metal mixture is T_{f}=30^{\circ} \mathrm{C}. The mass of the metal is m=0.2 \mathrm{~kg}, and the mass of water is M=0.5 \mathrm{~kg}. The specific heat of water is c_{w}=4200 \mathrm{~J} / \mathrm{kg}^{\circ} \mathrm{C}.

The specific heat cm of the metal is:

Option: 1

100 \mathrm{~J} / \mathrm{kg}^{\circ} \mathrm{C}


Option: 2

250.5 \mathrm{~J} / \mathrm{kg}^{\circ} \mathrm{C}


Option: 3

437.5 \mathrm{~J} / \mathrm{kg}^{\circ} \mathrm{C}


Option: 4

500 \mathrm{~J} / \mathrm{kg}^{\circ} \mathrm{C}


Answers (1)

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The heat lost by the hot metal is equal to the heat gained by the cold water. This can be expressed using the formula:

m \cdot c_{m} \cdot\left(T_{m}-T_{f}\right)=M \cdot c_{w} \cdot\left(T_{f}-T_{i}\right)

Given:

\begin{aligned} m & =0.2 \mathrm{~kg} \\ T_{m} & =150^{\circ} \mathrm{C} \\ M & =0.5 \mathrm{~kg} \\ T_{i} & =25^{\circ} \mathrm{C} \\ T_{f} & =30^{\circ} \mathrm{C} \\ c_{w} & =4200 \mathrm{~J} / \mathrm{kg}^{\circ} \mathrm{C} \end{aligned}

Solve for cm :

c_{m}=\frac{M \cdot c_{w} \cdot\left(T_{f}-T_{i}\right)}{m \cdot\left(T_{m}-T_{f}\right)}
 

Substitute the given values:

c_{m}=\frac{0.5 \mathrm{~kg} \cdot 4200 \mathrm{~J} / \mathrm{kg}^{\circ} \mathrm{C} \cdot\left(30^{\circ} \mathrm{C}-25^{\circ} \mathrm{C}\right)}{0.2 \mathrm{~kg} \cdot\left(150^{\circ} \mathrm{C}-30^{\circ} \mathrm{C}\right)}

Calculate the value of cm :

c_{m}=\frac{21000 \mathrm{~J} / \mathrm{kg}}{2400 \mathrm{~K}}=437.5 \mathrm{~J} / \mathrm{kg}^{\circ} \mathrm{C}

So, the specific heat cm of the metal is approximately 437.5 \mathrm{~J} / \mathrm{kg}^{\circ} \mathrm{C}.

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shivangi.bhatnagar

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