Which of the following is the correct formula to calculate percent by mass? [mass of solution (g) + mass of solute (g)] × 100 [mass of solute (g) − mass of solution (g)] × 100 [mass of solute (g) ÷ mass of solution (g)] × 100 [mass of solution (g) ÷ mass of solute (g)] × 100

C.  [Mass of solute (g) ÷ mass of solution (g)] × 100

Explanation:

For example  

If a solution of NaCl has a concentration of 1.50 M. The density of the solution is 1.06 g/mL. Then the concentration of solution by percent in mass?

Solution :  

Molarity is moles of solute present in 1L of its solution .

Hence the formula is

Molarity = (moles of solute) / (Volume of solution in L)  (unit is mol/L or M)

Let us convert the numerator and the denominator into mass in g

Numerator :                                  

mass = moles × molar mass

Denominator :                          

mass = density × volume

The formula to find mass percentage is

% mass =(mass of solute) / (mass of solution) × 100%

% mass of NaCl =(mass of solute) / (mass of solution) × 100%

= 8.28% (Answer)

a). in this case, dh> 0 and sd> 0. if t becomes larger, the term "-tds" will become more negative. at some point, it is possible that -dts will be more negative than the dh is positive, and the reaction will become spontaneous. this is probably the correct answer, but you should look at all of the other possibilities and make sure of that.