(1) Calcium gluconate is composed of four elements: carbon, hydrogen, oxygen, and calcium; the mass ratio of calcium to oxygen is 40: (16×7×2)=5: 28．

(2) The relative molecular mass of calcium gluconate is 40 (12×6 1×11 16×7)×2=430.

(3) The mass fraction of calcium in calcium gluconate is

40

430

×100≈9.3.

(4) The mass of calcium contained in each bottle is 600mg×9.3=55.8mg.

(5) Each bottle contains 600 mg of calcium gluconate [ca (c6h11o7) 2] and 30 mg of zinc gluconate [zn (c6h11o7) 2]. If his daily oral liquid intake contains 15 mg of gluconic acid Zinc, it also contains calcium gluconate [ca(c6h11o7)2] 300mg. The mass of calcium contained in each bottle is 600mg×9.3=55.8mg, then the mass of calcium taken in at the same time is 55.8mg÷2=27.9 mg.

So the answer is: (1) 4; 5:28; (2) 430; (3) 9.3; (4) 55.8; (5) 27.9.