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Answer : The change in internal energy is, 900 Joules.
Solution : Given,
Heat given to the system = +1400 J
Work done by the system = -500 J
Change in internal energy is equal to the sum of heat energy and work done.
Formula used :

where,
= change in internal energy
q = heat energy
w = work done
As per question, heat is added to the system that means, q is positive and work done by the system that means, w is negative.
Now put all the given values in the above formula, we get

Therefore, the change in internal energy is 900 J.
The change in internal energy depends on the heat energy and work done. As we will change in the heat energy and work done, then changes will occur in the internal energy. Hence, the energy is conserved.
Answer:
The mass percent refers to the mass of an element in a compound. It is one of the ways of expressing concentration. The mass percent of the solution provides the percentage of the amount of solute present in grams of solution.
The mass percentage of S=40.06 % and the molar mass of S= 32. By applying the formula of mass percent,we can calculate the molar mass of M.
The molar mass of M=159.76-64=95.76
We know that the element of molybdenum has molar mass of 96. Therefore, the element M is <u>Molybdenum.</u>
Answer:
-The stronger electrostatic forces of attraction between the oppositely charged ions causes the Sodium chloride to break apart until it completely dissolves in the water.
Explanation:
-Sodium Chloride has positively charged sodium ions,
and negatively charged chloride ions,
.
-Water on the other hand has positively charged Hydrogen ions,
and negatively charged Oxygen ions,
due to the difference in electroneganivity.
-When dissolved in water, the positively charged sodium ions will attract the partially negatively charged oxygen ions. The negatively charged chloride ions will be attracted to the positively charged hydrogen ions in the reaction as below:

Considering mass percentages, stars in the vicinity of the sun contain only 2% other elements by mass. Other than the main components, hydrogen and helium, stars have some heavier elements such as carbon, nitrogen, oxygen and iron. These elements are found near or in the star's core and are ejected into space when the star dies.