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Calculate the energy change (with the correct sign) when the temperature of 100.0 mL of liquid water decreases by 4.50∘C. energy change Calculate the mass of NH4​Cl needed to absorb the same amount of energy when dissolved in water. ΔHwolution ​(NH4​Cl)=844.39 J/mol.

User Ankur Garg
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Final answer:

The energy change when the temperature of 100.0 mL of water decreases by 4.5°C is -1892 J. The mass of NH4Cl needed to absorb the same amount of energy when dissolved in water is 119.86 g.

Step-by-step explanation:

To calculate the energy change when the temperature of 100.0 mL of liquid water decreases by 4.50∘C, we need to use the equation q = m * c * ΔT, where q is the energy change, m is the mass of the water, c is the specific heat capacity of water, and ΔT is the change in temperature.

The specific heat capacity of water is approximately 4.184 J/g°C. The mass of water can be calculated using its density, which is 1.00 g/mL. So, the mass of 100.0 mL of water is 100.0 g.

Plugging the values into the equation, we get q = (100.0 g) * (4.184 J/g°C) * (-4.50°C) = -1892 J. Therefore, the energy change when the temperature of 100.0 mL of liquid water decreases by 4.50∘C is -1892 J

To calculate the mass of NH4Cl needed to absorb the same amount of energy when dissolved in water, we can use the equation q = ΔH * n, where q is the energy change, ΔH is the enthalpy change of NH4HCl when dissolved in water, and n is the number of moles of NH4Cl.

Rearranging the equation to solve for n, we have n = q / ΔH. Plugging in the values from the question, we have n = -1892 J / 844.39 J/mol = -2.24 mol.

Since the number of moles cannot be negative, the absolute value of the number of moles is 2.24 mol.

The molar mass of NH4Cl is 53.49 g/mol. So, the mass of NH4Cl needed to absorb the same amount of energy when dissolved in water is (2.24 mol) * (53.49 g/mol) = 119.86 g.

User Totoro
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Final answer:

To calculate the energy change when the temperature of liquid water decreases, use the equation q = mcΔT. Given the specific heat capacity of water, convert the mL of water to grams and calculate the mass.

Step-by-step explanation:

To calculate the energy change when the temperature of 100.0 mL of liquid water decreases by 4.50°C, we can use the equation:

q = mcΔT

Where q is the energy change, m is the mass of the water, c is the specific heat capacity of water, and ΔT is the change in temperature.

Given that the specific heat capacity of water is 4.184 J/g°C, we need to convert the mL of water to grams and calculate the mass.

User Betina
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