Answer:
The sum of the molar masses of each isotope of the element.
The exothermic process is a process or reaction that involves a release of energy from the system to its surroundings in various forms usually through heat, light, electricity or sound. In the four given choices, when melting a copper, you try to immerse the metal in heaping coals of fire. The metal will absorb the thermal energy coming from the coal, thus, once you retrieve the metal back, light will be emitted from it as well as heat.
Therefore, the answer is B. MELTING OF COPPER
Hydrofluoric acid is a solution of hydrogen fluoride (HF) in water. Solutions of HF are colourless, acidic and highly corrosive. It is used to make most fluorine-containing compounds; examples include the commonly used pharmaceutical antidepressant medication fluoxetine (Prozac) and the material PTFE (Teflon).
Considering the definition of molarity, the molar concentration is 0.294 
.
Molarity reflects the concentration of a solution indicating the number of moles of solute that are dissolved in a given volume.
The molarity of a solution is calculated by dividing the moles of the solute by the volume of the solution:
Molarity is expressed in units .
In this case, you know:
- amount of moles of solute= 0.250 moles
- volume= 0.850 L
Replacing in the definition of molarity:
Solving:
molarity= 0.294
Finally, the molar concentration is 0.294 .
Learn more about molarity with this example: brainly.com/question/15406534?referrer=searchResults
