Answer : The molal freezing point depression constant of liquid X is, 
Explanation : Given,
Mass of urea (solute) = 5.90 g
Mass of liquid X (solvent) = 450 g = 0.450 kg
Molar mass of urea = 60 g/mole
Formula used :
where,
= change in freezing point
= freezing point of solution = 
= freezing point of liquid X = 
i = Van't Hoff factor = 1 (for non-electrolyte)
= Molal-freezing-point-depression constant = ?
m = molality
Now put all the given values in this formula, we get
Therefore, the molal freezing point depression constant of liquid X is,
(4.4273 × 10¹⁰)/(5.3668 × 10³) = 0.824 94 × 10⁷ = 8.2494 × 10⁶
Answer: B. a chemical change
Explanation:
In a high-mass star, hydrogen fusion occurs via the CNO (Carbon-Nitrogen-Oxygen) cycle.
According to the life cycle of a star, there are three main phases in the life of a star: The initial phase (a quick phase), short phase or supergiant phase and death phase or supernova explosion.
the CNO cycle means Carbon-Nitrogen-Oxygen cycle and this process tale place during main sequence phase.
In this phase, hydrogen fuses into helium as a result of six different reaction taking place inside a star.
The first step of the sequence begins when the nucleus of carbon 12 isotope emits gamma rays after capturing a proton and produces nitrogen-13.
This whole cycle is known as stellar nucleosynthesis.
If you need to learn more about Carbon-Nitrogen Cycle click here:
brainly.com/question/13022835
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