Answer:

Explanation:
Hello!
In this case, according to the Avogadro's number, it is possible to compute the atoms of Kr in 2.00 moles as shown below:

Best regards!
Molecular mass= (14.01∗1)+(1.008∗3)
14.01+3.024=17.03g/mol
Electrons are responsible for the transfer of charge.
The heat cause 300g water temperature increase from 20 to 26 celcius. The heat transferred would be: 300g * (26 °C -20 °C) *4.2 joule/gram °C= 7560J
The unknown substance is added to the water, so its final temperature should be the same as the water. The calculation would be:
7560J= 124g * (100-26)* specific heat
specific heat= 7560J / 124g / 74 °C= 0.8238 J/gram °C