An 40.39 g sample of aluminum is placed on a 26.17 g sample of copper initially

Question

An 40.39 g sample of aluminum is placed on a 26.17 g sample of copper initially at 106.37oC. If the heat is only transferred between the metals (with no loss to the surroundings) and the final temperature of both metals is 49.5oC, what is the inital temperature (in oC) of aluminum?

How much heat (in kJ) is evolved (under standard conditions) when 184.78 g of copper reacts to form copper(II) oxide?

How much heat (in kJ) is evolved when 60.26 g of water cools and freezes from 59.63oC to 0oC?

What is the change in enthalpy (in kJ) under standard conditions when 8.186 g of ethane is combusted?

Explanation / Answer

According to chegg rules we have to answer only first one problem

Given that;

An 40.39 g sample of aluminum is placed on a 26.17 g sample of copper

The molar heat capacities of Al = 24.3 J/(mol·°C)

The molar heat capacities of Cu = 24.5 J/(mol·°C),

Temperature of Cu = 106.37 °C

Final Temperature of both metal = 49.5oC °C

We know that;

-heat lost by Cu = heat gained by Al

first calculate the number of moles of both metal as follows:

number of mole = amount in g / molar mass

moles Al = 40.39 g / 26.98 g/mole = 1.50 moles
moles Cu = 26.17 g / 63.55 g/mole = 0.42 moles

- heat lost by Cu = heat gained by Al

-(0.42 moles Cu x 24.5 J/mole-ºC (49.5oC -106.37 °C ) = 1.50 moles Al x 24.3 J/mole-ºC) (Ti - 49.5oC)

-585.1923 = 36.45 (Ti - 49.5oC)

-585.1923 = 36.45 Ti – 1804.275 oC

36.45 Ti= 1219.0827

Ti = 33.45 oC

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