Answer:
16.5 g
Explanation:
When a nonvolatile compound is dissolved in a pure solvent, the freezing point of the solvent is reduced, because the interaction solvent-solute requires more energy to be joined, and so, it freezes. This property is called cryoscopy, and the temperature change (ΔT) can be calculated by:
ΔT = Kc*W*i
Where Kc is the cryoscopy constant of the solute X, W is the molality of the solution, and i is the van't Hoff factor, which determines the percent of the solute that is dissolved. For organic molecules, such as alanine, i = 1.
The molality is the number of moles of the solute divided by the mass (in kg) of the solvent (1200 g = 1.2 kg). The molar mass of alanine is 89.09 g/mol, and the number of moles of it is the mass divided by the molar mass:
n = 45.8/89.09
n = 0.5141 mol
W = 0.5141/1.2 = 0.4284 mol/kg
So, Kc of X is:
4.10 = Kc*0.4284*1
Kc = 9.57 °C.kg/mol
So, if now sodium chloride is added to X, and the variation temperature is the same, and i = 1.82:
4.10 = 9.57*W*1.82
W = 0.2354 mol/kg
The number of moles of the solute is then:
W = n/1.2
0.2354 = n/1.2
n = 0.2825 mol
The molar mass of sodium chloride is 58.44 g/mol, thus the mass is the molar mass multiplied by the number of moles:
m = 58.44*0.2825
m = 16.5 g
Students who spend less time studying after school, get lower math grades. Option D.
<h3>What is a research investigation?</h3>
In science, a research investigation is an organized inquiry made into phenomena in order to logically understand them. The investigation follows an established procedure, otherwise known as the scientific method.
The original investigation by the student has to do with factors that affect math grades. Conclusions are usually drawn from the aim and objectives of the research. Thus, the conclusion must relate to the aim of the research in a logical way.
The only option that fits in logically going by the aim of the investigation is that students who spend less time studying after school, get lower math grades.
More on research investigations can be found here: brainly.com/question/4118656
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What subject is this again ? If I know now then I would have a better understanding of what I’m gonna answer so you don’t get it wrong !
Answer:
An example is the reaction of ammonia with boron trifluoride. Figure 2. Ammonia and boron trifluoride. Boron trifluoride is the Lewis acid, while ammonia is again the Lewis base. As there is no hydrogen ion involved in this reaction, it qualifies as an acid-base reaction only under the Lewis definition.