The main pieces of evidence that an exothermic reaction has occurred is an increase in temperature due to the release of energy, a release of energy in the form of light, or a release of gas.
The first law of thermodynamics characterises the two types of energy transfer, as heat and as thermodynamic. The final internal (thermal) energy of the system is 1,500 J.
<h3>What is internal energy?</h3>
The energy present in a system itself for conducting reactions is called internal energy.
Given,
- Heat entering system (Q) = 700 J
- Work done by the piston (W) = 400
- Initial energy
= 1200 J
According to the <u>first law of thermodynamics</u>:

Substituting values in the above equation:

Therefore, option D. 1500 J is the final energy.
Learn more about internal energy here:
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Answer:
Question 1 is 21.0g
Explanation:
50 x 4.18 x 3.1 / 0.444 / 69.6= 21.0
Molality= mol/ Kg
if we assume that we have 1 kg of water, we have 3.19 moles of solute.
the formula for mole fraction --> mole fraction= mol of solule/ mol of solution
1) if we have 1 kg of water which is same as 1000 grams of water.
2) we need to convert grams to moles using the molar mass of water
molar mass of H₂O= (2 x 1.01) + 16.0 = 18.02 g/mol
1000 g (1 mol/ 18.02 grams)= 55.5 mol
3) mole of solution= 55.5 moles + 3.19 moles= 58.7 moles of solution
4) mole fraction= 3.19 / 58.7= 0.0543
Answer: the answer is number 3 which is 6