True or false. the gleaming metallic appearance of the gateway arch in st. louis, missouri, comes from the stainless steel used in its construction. this steel is made mostly of iron, but it also contains 19% (by mass) chromium and 9.0% (by mass) nickel.

True

Explanation:

This will mean that from the assumed mass Chromium (Cr) = 19%, and Nickel (Ni) = 9%

This therefore means that Iron (Fe) = 72%

If we change this to mole we will further see that the ratio of Cr to Ni atoms is about 2.4 to 1  

1. for the first question, we must find the mass of the anhydrous salt, mgso₄. the molar mass for mgso₄·7h₂o is 246.47 g/mol, while that of mgso₄ is 120.37 g/mol.7.834 g mgso₄·7h₂o * 1 mol mgso₄·7h₂o/246.47 g * 1 mol mgso₄/1 mol mgso₄·7h₂o * 20.37 g mgso₄/mol = 0.647 g mgso₄

2. mass of water = mass of sample - mass of anhydrous salemass of water = 7.834 - 0.647 = 7.19 gpercent water in hydrate = 7.19/7.834 * 100 = 91.74%