Elements are substances that contain only 1 kind of atom.
Answer:

Explanation:
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In this case, the undergoing chemical reaction is:

In such a way, the mercury II sulfate (molar mass 296.65g/mol) is in a 1:1 molar ratio with the mercury II chloride (molar mass 271.52g/mol), for that reason the stoichiometry to find mass in grams of mercury II chloride turns out:

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Answer:
H- hydrogen
Explanation: Hydrogen is in the first group meaning that it only has 1 valence electron and 1 energy level
<u>Answer:</u> The molality of magnesium chloride is 1.58 m
<u>Explanation:</u>
To calculate the molality of solution, we use the equation:

Where,
= Given mass of solute (magnesium chloride) = 75.0
= Molar mass of solute (magnesium chloride) = 95.21 g/mol
= Mass of solvent = 500.0 g
Putting values in above equation, we get:

Hence, the molality of magnesium chloride is 1.58 m