Question

Calculate the mass of chromium metal produced when 425.0mL of 0.25M chromium(ll) nitrate reacts with a strip of zinc that remains in excess. Also write and balance an equation.

Answer 1

The balanced chemical equation for the production of chromium metal from the reaction of chromium(ll) nitrate reacts with a strip of zinc is:

3 Zn + 2 Cr(NO₃)₃ → 2 Cr + 3 Zn(NO₃)₂

This is a redox reaction, which is a chemical reaction in which one or more electrons are transferred between the reagents, causing a change in their oxidation states. In the proposed reaction, Cr oxidation state goes from +3 to 0, becoming metallic chromium, while Zn goes from being Zn⁰ to Zn²⁺.

The mass of chromium metal produced in the above reaction will be,

425.0 mL x
`(1 L)/(1000 mL)` x
`(0.25 mol Cr(NO_(3))_(3)  )/(1 L)` x
`(2 mol Cr  )/(2 mol Cr(NO_(3))_(3) )` x
`(51.9961 g Cr)/(1 mol Cr)` = 5.52 g

So, the mass of chromium metal produced when 425.0mL of 0.25M chromium(ll) nitrate reacts with a strip of zinc that remains in excess is 5.52 g of Cr.