You have to use density=mass/volume formula:

Solve for x and you get
2282.75 grams
Answer:
[KBr] = 454.5 m
Explanation:
m is a sort of concentration that indicates the moles of solute which are contianed in 1kg of solvent.
In this case, the moles of solute are 0.25 moles.
Let's determine the mass of solvent in kg.
Density of heavy water, solvent, is 1.1 g/L and our volume is 0.5L.
1.1 g = mass of solvent / 0.5L, according to density.
mass of solvent = 0.5L . 1.1g/L = 0.55 g
We convert the mass to kg → 0.55 g . 1kg /1000g = 5.5×10⁻⁴ kg
m = mol/kg → 0.25 mol /5.5×10⁻⁴ kg = 454.5 m
Answer: F. Endothermic…………………
Explanation:
The scientific method involves making observations and asking questions. Scientists form hypotheses based on these observations and then develop controlled experiments to collecting and analyze data. Using this data, they are able to draw conclusions and form questions for new scientific research.
:)ᴍᴀʀᴋ ᴀꜱ ʙʀᴀɪɴʟɪꜱᴛ
2.13x10^24 is the answer.