500 mL solution of calcium chloride with a concentration of 0.75 mol/L. The mass of solute needed to make this solution is ___ ___ ___ ___ g.

41.63g

Explanation:

Given parameters:

Volume of CaCl₂  = 500mL  = 0.5L

Concentration  = 0.75mol/L

Unknown:

Mass of the solute needed = ?

Solution:

The mass of the solute can be derived using the expression below;

     Mass  = number of moles x molar mass

But,

   Number of moles  = Concentration x Volume

So;

     Mass  = Concentration x Volume x molar mas

Molar mass of CaCl₂  = 40 + 2(35.5) = 111g/mol

     Mass  = 0.75 x 0.5 x 111 = 41.63g

answer : one can design an experiment using a liquid and an additive that can be added to the liquid and observe the chemical changes in the reaction species.

one would need a beaker which is filled with a known amount of the liquid in which thermometer is placed to measure the temperature changes; after addition of the additive to the liquid solution one can note down the temperature change and find whether the reaction is endothermic or exothermic in nature. by subtracting the initial temperature value with the final temperature one can find the temperature changes.

various combinations of liquid and additive can be used. liquid in this case can be a known quantity of water and additives can be epsom salt or without epsom salt the experiment can be conducted to notice the changes. water and ice, hydrogen peroxide and dry yeast, vinegar and baking soda,etc.