Energy and specific heat

1. draw a graph of an exothermic reaction. label reactants, products and ∆h.

2. calculate the amount of energy required to raise the temperature of 3.00g of gold from 45.9 to 93.0°c.

3. 1.70g of a silvery metal requires 1000.j of energy to change its temp from 298k to 2749k. is the metal pure silver?

1. Kindly, see the attached image.

2. 18.369 J.

3. Yes, the metal is pure silver.

Explanation:

1. Draw a graph of an exothermic reaction. Label reactants, products and ∆H.

Kindly, see the attached image that shows the graph of an exothermic reaction.

2. Calculate the amount of energy required to raise the temperature of 3.00 g of gold from 45.9 to 93.0°C.

To solve this problem, we can use the relation:

Q = m.c.ΔT.

Where, Q is the amount of energy required to raise the temperature of gold (J).

m is the mass of the gold (m = 3.0 g).

c is the specific heat of gold (c = 0.13 J/g.°C).

ΔT is the temperature difference between the initial and final T (ΔT = 93.0 °C - 45.9 °C = 47.1 °C).

∴ Q = m.c.ΔT = (3.0 g)(0.13 J/g.°C)(47.1 °C) = 18.369 J.

3. 1.70 g of a silvery metal requires 1000.0 J of energy to change its temp from 298 K to 2749 K. Is the metal pure silver?

To determine wither the metal is pure or not, we should calculate the specific heat (c) of Ag and compare it with the reported value in the table.

As mentioned in details in the second point, we can use the relation:

Q = m.c.ΔT

Q = 1000.0 J, m = 1.70 g, ΔT = 2749 - 298 = 2451 °C.

∴ c = Q/(m.ΔT) = (1000.0 J)/(1.70 g)(2451 °C) = 0.239 J/g.°C ≅ 0.24 J/g.°C.

The calculated value is the same as the value reported in the table, so the metal is pure silver.

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Explanation: