Question

Which of the following statements are true? For any false statements, explain.

1. Nitric acid reacts with magnesium metal and copper metal.

2. Sulfuric acid and nitric acid react with cupric oxide.

3. Heating cupric hydroxide produces copper metal.

4. Copper metal reacts with magnesium ion. Mg ^2+.

5. Cupric ion is blue and magnesium ion is white in aqueous solution.

6. Sulfuric acid reacts with magnesium metal and copper metal.

I got

1. False

2. False

3. True

4. True

5. True

6. False

Answer 1

1) Cu_(s) + 4HNO_3(aq)   Cu(NO₃)_2(aq) + 2NO_2(g) + 2H₂O_(l)

The initial green colour is associated with the copper when ligated by nitrate ions in high concentration in the acid.* As water is added, it displaces the nitrate ions producing the characteristic blue colour in the fountain.

Mg + 2HNO3 --> Mg(NO3)2 + H2 Heating

2) 8HNO3(aq) + 3Cu(s) + O2(g) >>> 3Cu(NO3)2(aq) + 4H2O(l) + 2NO2(g)

CuO(s) + H2SO4(aq) >>> CuSO4(aq) + H2O(l)

3) H2 + CuO -> Cu + H2O

4)

adding magnesium to blue copper(II) sulphate solution, the blue colour fades as colourless magnesium sulphate is formed and brown bits of copper metal form a precipitate:

• eg magnesium + copper sulphate ==> magnesium sulphate + copper
• • Mg + CuSO₄ ==> MgSO₄ + Cu
  • • Mg(s) + CuSO₄(s) ==> MgSO₄(s) + Cu(s)

5)

magnesium ion: Mg2+(aq) + 2OH-(aq) ==> Mg(OH)2(s)gives a white precipitate of magnesium hydroxide, which is not soluble in excess of either NH3 or NaOH. You could distinguish Mg from Ca with a flame test or ammonia test above.

copper(II) ion: Cu2+(aq) + 2OH-(aq) ==> Cu(OH)2(s) gives a blue/turquoise ppt. of copper(II) hydroxide, which dissolves in excess ammonia to give a deep blue solution of an ammine complex, but copper(II) hydroxide is NOT soluble in excess NaOH. Cu(OH)2(s) + 4NH3(aq) ==> [Cu(NH3)4]2+(aq) + 2OH-(aq) 6) magnesium + sulfuric acid ? magnesium sulfate + hydrogen Mg + H2SO4 ? MgSO4 + H2 cu + H2SO4 ? cuSO4 + H2

1)true

2)false

3)false

4)false

5)true

6)true