Answer: With atomic number 20, calcium atoms have 20 positive protons, and the ion has only 18 electrons, which means the net charge is +2. Calcium ions are essential for muscle contractions, nerve impulses, and bone maintenance.
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The answer to this question would be D. Hydrophilic.
The word hydrophilic mean attracted by water. That means the molecule has a force to attract water molecule, thus be able to dissolve in water. The polarity of the molecule would determine whether a molecule hydrophilic or not.
Its opposite would be hydrophobic which the molecule can't dissolve in water. One example of this would be oil or fat. That is why sometimes it is called lipophilic too.
Answer : The final pressure of the gas will be, 26.8 kPa
Explanation :
According to the Boyle's law, the pressure of the gas is inversely proportional to the volume of the gas at constant temperature of the gas and the number of moles of gas.

or,

or,

where,
= initial pressure of the gas = 209 kPa
= final pressure of the gas = ?
= initial volume of the gas = 10.0 L
= final volume of the gas = 78.0 L
Now put all the given values in this formula, we get the final pressure of the gas.


Therefore, the final pressure of the gas will be, 26.8 kPa