(3) the water to the ice cubes
This is so because the ice cubes are colder compared to their surrounding objects.
They absorb the heat from the water, cooling it, therefore vanishing(melting).
The water molecules are not completely removed so additional heating is required.
Explanation:
We have the copper (II) sulfate pentehydrate with the chemical formula CuSO₄ · 5H₂O.
molar mass of CuSO₄ · 5H₂O = 159.6 + 5 × 18 = 249.6 g/mole
Knowing this, we devise the following reasoning:
if in 249.6 g of CuSO₄ · 5H₂O there are 90 g of H₂O
then in 8 g of CuSO₄ · 5H₂O there are Y g of H₂O
Y = (8 × 90) / 249.6 = 2.88 g of water
mass of dried CuSO₄ = mass of CuSO₄ · 5H₂O - mass of H₂O
mass of dried CuSO₄ = 8 - 2.88 = 5.12 g
5.12 g is less that the weighted mass of 6.50 g. We deduce from this that the sample needs additional heating in order to remove all the water (H₂O) molecules.
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hydrates
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The main purpose of scientific methods, is to show the variations of the topic you are doing in science and how you are proving it to be that way.
This problem applies Hess' Law to come up with the final reaction from a series of reactions given. Equation (1) stays as it is. Equation (2) should be inverted and divided by 2. Equation (3) is simply divided by 2. The energies should also correspond to the operations. Adding the net energies of each reaction, the total energy is 155.65 kJ. Hence, the answer is A.
