Determine the mass % of a NaCl solution if 58.5 grams of NaCl was dissolved in 50 ml of water (assume the density of water to be
1 answer:
Considering the definition of percentage by mass and density, the percentage by mass of a NaCl solution is 53.917%.
<h3>Percentage by mass</h3>The percentage by mass expresses the concentration and indicates the amount of mass of solute present in 100 grams of solution.
In other words, the percentage by mass of a component of the solution is defined as the ratio of the mass of the solute to the mass of the solution, expressed as a percentage.
The percentage by mass is calculated as the mass of the solute divided by the mass of the solution, the result of which is multiplied by 100 to give a percentage. This is:
Density is defined as the property that matter, whether solid, liquid or gas, has to compress into a given space.
In other words, density is a quantity that allows us to measure the amount of mass in a certain volume of a substance. Then, the expression for the calculation of density is the quotient between the mass of a body and the volume it occupies:
In this case, you know:
- mass of solute= 58.5 grams
- volume of water= 50 mL
- density of water= 1
- mass of solution= mass of solute + mass of water
Replacing in the definition of density, you get the mass of water:
Solving:
mass of water= 1 × 50 mL
<u><em>mass of water= 50 grams</em></u>
Then, you get that the mass of solution is calculated as:
mass of solution= mass of solute + mass of water
mass of solution= 58.5 grams + 50 grams
<u><em>mass of solution= 108.5 grams</em></u>
So, the percentage by mass is calculated as:
<u><em>percentage by mass= 53.917%</em></u>
Finally, the percentage by mass of a NaCl solution is 53.917%.
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Answer :
(A) ΔH is positive and ΔS is negative → (2) Spontaneous in reverse at all temperatures
(B) ΔH is positive and ΔS is positive → (3) Spontaneous as written above a certain temperature
(C) ΔH is negative and ΔS is positive → (1) Spontaneous as written at all temperatures
(D) ΔH negative and ΔS is negative → (4) Spontaneous as written below a certain temperature
Explanation :
According to Gibb's equation:
= Gibbs free energy
= enthalpy change
= entropy change
T = temperature in Kelvin
As we know that:
= +ve, reaction is non spontaneous
= -ve, reaction is spontaneous
= 0, reaction is in equilibrium
(A) ΔH is positive and ΔS is negative.
The reaction is non-spontaneous at all temperatures or spontaneous in reverse at all temperatures.
(B) ΔH is positive and ΔS is positive.
(at low temperature) (non-spontaneous)
(at high temperature) (spontaneous)
The reaction is spontaneous as written above a certain temperature.
(C) ΔH is negative and ΔS is positive.
The reaction is spontaneous as written at all temperatures
(D) ΔH is negative and ΔS is negative.
(at high temperature) (non-spontaneous)
(at low temperature) (spontaneous)
The reaction is spontaneous as written below a certain temperature.