The atomic number of copper is 29.
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Answer:
55.9 g KCl.
Explanation:
Hello there!
In this case, according to the definition of molality for the 0.500-molar solution, we need to divide the moles of solute (potassium chloride) over the kilograms of solvent as shown below:

Thus, solving for the moles of solute, we obtain:

Since the density of water is 1 kg/L, we obtain the following moles:

Next, since the molar mass of KCl is 74.5513 g/mol, the mass would be:

Regards!
Answer:
the smallest mass of material that can sustain a chain reaction
Explanation:
Critical mass refers to the smallest possible mass of a fissionable material that can sustain a chain reaction
Unstable nucleus is your answer