(a) What amount of heat (in joules) is required to raise the temperature of $1 \mathrm{~g}$ of water by 1 kelvin? (b) What amount of heat (in joules) is required to raise the temperature of 1 mole of water by 1 kelvin? (c) What is the heat capacity of \(370 \mathrm{~g}\) of liquid water? (d) How many kJ of heat are needed to raise the temperature of $5.00 \mathrm{~kg}\( of liquid water from 24.6 to \)46.2^{\circ} \mathrm{C} ?$

Short Answer

Expert verified
(a) 4.18 J (b) 75.24 J (c) 1546.6 J/K (d) 453.1 kJ

Step by step solution

01

(a) Calculate the heat required to raise the temperature of 1g of water by 1K

Using the heat equation given above: \[Q = mc\Delta T\] The mass of water, \(m\) is 1 g, the specific heat capacity of water, \(c\) is \(4.18 \frac{\mathrm{J}}{\mathrm{g} \cdot \mathrm{K}}\) and the change in temperature, \(\Delta T\) is 1 K. Substituting these values into the equation, we get: \[Q = 1 \times 4.18 \times 1\] \[Q = 4.18~ \mathrm{J}\] So, the amount of heat required is 4.18 J.
02

(b) Calculate the heat required to raise the temperature of 1 mole of water by 1K

First, we need to find the mass of 1 mole of water. The molecular weight of water is approximately 18 g/mol. Therefore, 1 mole of water weighs 18 g. Now, using the heat equation: \[Q = mc\Delta T\] The mass of water, \(m\) is 18 g, the specific heat capacity of water, \(c\) is \(4.18 \frac{\mathrm{J}}{\mathrm{g} \cdot \mathrm{K}}\) and the change in temperature, \(\Delta T\) is 1 K. Substituting these values into the equation, we get: \[Q = 18 \times 4.18 \times 1\] \[Q = 75.24~ \mathrm{J}\] So, the amount of heat required is 75.24 J.
03

(c) Calculate the heat capacity of 370g of liquid water

The heat capacity of a substance is given by the product of its mass and its specific heat capacity: \[C = mc\] Where \(C\) is the heat capacity, \(m\) is the mass, and \(c\) is the specific heat capacity. For 370 g of water, the specific heat capacity, \(c\) is \(4.18 \frac{\mathrm{J}}{\mathrm{g} \cdot \mathrm{K}}\). So, the heat capacity of 370 g of water is: \[C = 370 \times 4.18\] \[C = 1546.6~\frac{\mathrm{J}}{\mathrm{K}}\] So, the heat capacity of 370 g of liquid water is 1546.6 J/K.
04

(d) Calculate the heat required to raise the temperature of 5.00 kg of liquid water from 24.6°C to 46.2°C

First, we need to find the change in temperature, \(\Delta T\). The initial temperature is 24.6°C, and the final temperature is 46.2°C. Therefore, the change in temperature is: \[\Delta T = T_{f} - T_{i} = 46.2 - 24.6 = 21.6~\mathrm{K}\] Next, we use the heat equation: \[Q = mc\Delta T\] The mass of water, \(m\) is 5.00 kg, the specific heat capacity of water, \(c\) is \(4186 \frac{\mathrm{J}}{\mathrm{kg} \cdot \mathrm{K}}\) and the change in temperature, \(\Delta T\) is 21.6 K. Substituting these values into the equation, we get: \[Q = 5.00 \times 4186 \times 21.6\] \[Q = 453124.8 ~\mathrm{J}\] To convert this to kJ, divide by 1000: \[Q = \frac{453124.8}{1000}\] \[Q = 453.1~ \mathrm{kJ}\] So, 453.1 kJ of heat is needed to raise the temperature of 5.00 kg of liquid water from 24.6°C to 46.2°C.

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Most popular questions from this chapter

We can use Hess's law to calculate enthalpy changes that cannot be measured. One such reaction is the conversion of methane to ethane: $$ 2 \mathrm{CH}_{4}(g) \longrightarrow \mathrm{C}_{2} \mathrm{H}_{6}(g)+\mathrm{H}_{2}(g) $$ Calculate the \(\Delta H^{\circ}\) for this reaction using the following thermochemical data: $$ \begin{aligned} \mathrm{CH}_{4}(g)+2 \mathrm{O}_{2}(g) & \longrightarrow \mathrm{CO}_{2}(g)+2 \mathrm{H}_{2} \mathrm{O}(l) & \Delta H^{\circ} &=-890.3 \mathrm{~kJ} \\ 2 \mathrm{H}_{2}(g)+\mathrm{O}_{2}(g) & \longrightarrow 2 \mathrm{H}_{2} \mathrm{O}(l) & \Delta H^{\circ} &=-571.6 \mathrm{~kJ} \\ 2 \mathrm{C}_{2} \mathrm{H}_{6}(g)+7 \mathrm{O}_{2}(g) & \longrightarrow 4 \mathrm{CO}_{2}(g)+6 \mathrm{H}_{2} \mathrm{O}(l) & \Delta H^{\circ} &=-3120.8 \mathrm{~kJ} \end{aligned} $$

Calculate \(\Delta E\) and determine whether the process is endothermic or exothermic for the following cases: \((\mathbf{a}) q=0.763 \mathrm{~kJ}\) and \(w=-840 \mathrm{~J}\). (b) A system releases \(66.1 \mathrm{~kJ}\) of heat to its surroundings while the surroundings do \(44.0 \mathrm{~kJ}\) of work on the system.

(a) Which releases the most energy when metabolized, \(1 \mathrm{~g}\) of carbohydrates or \(1 \mathrm{~g}\) of fat? (b) A particular chip snack food is composed of \(12 \%\) protein, \(14 \%\) fat, and the rest carbohydrate. What percentage of the calorie content of this food is fat? (c) How many grams of protein provide the same fuel value as \(25 \mathrm{~g}\) of fat?

Butane \(\mathrm{C}_{4} \mathrm{H}_{10}(l)\) boils at $-0.5^{\circ} \mathrm{C} ;\( at this temperature it has a density of \)0.60 \mathrm{~g} / \mathrm{cm}^{3}\(. The enthalpy of formation of \)\mathrm{C}_{4} \mathrm{H}_{10}(g)\( is \)-124.7 \mathrm{~kJ} / \mathrm{mol},$ and the enthalpy of vaporiza- tion of \(\mathrm{C}_{4} \mathrm{H}_{10}(l)\) is $22.44 \mathrm{~kJ} / \mathrm{mol} .\( Calculate the enthalpy change when \)1 \mathrm{~L}$ of liquid \(\mathrm{C}_{4} \mathrm{H}_{10}(l)\) is burned in air to give \(\mathrm{CO}_{2}(g)\) and \(\mathrm{H}_{2} \mathrm{O}(g) .\) How does this compare with \(\Delta H\) for the complete combustion of \(1 \mathrm{~L}\) of liquid methanol, \(\mathrm{CH}_{3} \mathrm{OH}(l) ?\) For $\mathrm{CH}_{3} \mathrm{OH}(l),\( the density at \)25^{\circ} \mathrm{C}\( is \)0.792 \mathrm{~g} / \mathrm{cm}^{3},\( and \)\Delta H_{f}^{\circ}=-239 \mathrm{~kJ} / \mathrm{mol}$.

From the enthalpies of reaction $$ \begin{aligned} \mathrm{H}_{2}(g)+\mathrm{F}_{2}(g) & \longrightarrow 2 \mathrm{HF}(g) & & \Delta H=-537 \mathrm{~kJ} \\ \mathrm{C}(s)+2 \mathrm{~F}_{2}(g) & \longrightarrow \mathrm{CF}_{4}(g) & & \Delta H=-680 \mathrm{~kJ} \\ 2 \mathrm{C}(s)+2 \mathrm{H}_{2}(g) & \longrightarrow \mathrm{C}_{2} \mathrm{H}_{4}(g) & & \Delta H=+52.3 \mathrm{~kJ} \end{aligned} $$ calculate \(\Delta H\) for the reaction of ethylene with \(\mathrm{F}_{2}\) : $$ \mathrm{C}_{2} \mathrm{H}_{4}(g)+6 \mathrm{~F}_{2}(g) \longrightarrow 2 \mathrm{CF}_{4}(g)+4 \mathrm{HF}(g) $$

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