Why there are two chloride ions for every calcium ion

The valency of calcium is +2

Explanation:

Calcium is in group two. The members of group two are divalent metals that loose two electrons to form M^2+.

Since they form M^2+, they form ionic bonds with two uninegative ions. Chlorine is in group 17. This implies that its valency is -1 and it accepts one electron when it participates in an ionic bond.

Hence it will take two chlorine atoms to receive two electrons from one calcium atom in an ionic bond making the ratio of calcium to chlorine in the compound 2:1.

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water at room temperature is flowing through a pipe with pressure taps located 10 ft apart along one section of the pipe, which are connected to a mercury (s=13.6) manometer.