A carbonate because the oxygen neutralizes the reactive coding of the calcium in its original form.
4 significant figures. Use a rule called the Atlantic-Pacific rule where if the period is absent (Atlantic), you would start counting the numbers from right to left. If the period is present (Pacific), then start counting the numbers from left to right. Since the period is present, start from 5 and there are 4 digits including 5.
It is kept constant
There is the answer if it helped
Yes. Look up Newton’s laws of physics. That should help
