Question

5. Which is the reducing agent in the following redox reaction? CuSO4 + Zn - > Cu + ZnSO. a) CuSO4 b) Zn c) ZnSO4 d) Cu 6. The oxidation number of manganese (Mn) in Mno, is; a) + 8 - 6 - 7 c) + 7 d) -8 7. Which of the following is insoluble in water? a) Ca(NO3) 2 b ) NaSO4 c) NH4Cl d) AgCI 8. What are the spectator ions in the reaction below? Ca(NO3)2 + Na2CO3 -> CaCO3 + 2 NaNO3 b) Nat & NO; c) Na& CO32- a) Ca & NO; d) Cat & CO32- 9. What is the mass of NaOH is needed to prepare 500 ml of 0.2 M NaOH solution? a) 40.0 g b) 10.0 g c) 4.0 g d) none of them

Answer 1

5) Reducing agent is the one which donates electrons: here Zn⁰ is becoming Zn⁺² , that means it donated 2 electrons to Cu.

6) MnO₄^- here the oxidation number of Mn is calculated as: X+4(-2)= -1 ===> X= +7. (Since the oxidation state of O is (-2)

7) The Na+ , K+ , and ammonium (NH4 + ) ions form soluble salts, also the nitrate (NO3 - ) ion forms soluble salts. Therefore the AgCl is the insoluble one. AgCl forms an opaque white precipitate

8)A spectator ion is an ion that exists in the same form on both the reactant and product sides of a chemical reaction. Spectator ions may be either cations (positively-charged ions) or anions (negatively-charged ions). The ion is unchanged on both sides of a chemical equation and does not affect equilibrium. SO HERE THE UNCHANGED IONS ARE THE ONES WHOSE SOLUBILITY DOESNT CHANGE THEY ARE Na⁺ & NO₃^-. THE CaCO₃ becomes a precipitate

9) Molar mass of NaOH is (23+16+1=40g/mol). 0.2M means 0.2moles/litre. Therefore in 500ml (i.e 0.5lit) we have 0.1 moles. That means 40/10=4gms is needed to make the asked solution

10)M₁V₁=M₂V₂ . 250*0.5=X*5===> X=25ml