To determine the amount of heat needed to evaporate a certain amount of water at its boiling point, we use the equation,
H = m(Hv)
where H is the heat, m is the mass (in grams), and Hv is the latent heat of vaporization. Substituting the known values,
H = (105 g)(540 cal/g)
H = 56700 cal
H = 56.7 kcal
Answer: 56.7 kcal
Answer : The final temperature of the copper is, 
Solution :
Formula used :
where,
Q = heat gained = 299 cal
m = mass of copper = 52 g
c = specific heat of copper = 
= final temperature = ?
= initial temperature = 
Now put all the given values in the above formula, we get the final temperature of copper.
Therefore, the final temperature of the copper is,
<span>The option A is correct answer. The isotopes are X and Y. The isotopes are those which have same atomic number but different mass number. Since atomic number has same number of protons or electrons. Thus, isotopes have same number of protons or electrons. Therefore, X and Y are isotopes.</span>
