It's Synthesis, single replacement is incorrect.
The answer to this question is bohr Greek
So the question is asking to compute the volume of a rectangular prism with a length of 5.6 cm, width of 2.1 cm and a height of 6.6 cm, and base on the said given and using the formula in getting the volume of a rectangular prism, the volume 77.62 cm^3. I hope this would help.
Unbalanced it should be 2Zn+2Hcl=2ZnCl2+H2
Mass / volume = density
30.943g / 35ml = 0.88408571g/ml