Question

need all questions answered please !!!!!!

1. The following reaction is used to generate hydrogen gas in the laboratory: Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g). If 243 mL of hydrogen gas is collected at 25°C and has a total pressure of 745 mm Hg, calculate the mass of hydrogen produced. Vapor pressure of water at 25°C is 23.78 mm Hg. (2 Pts.) 2. Sulfurous acid can form water and sulfur dioxide upon heating. How much sulfur dioxide is formed from 2.20 g of sulfurous acid? (2 Pts.) H2SO3 + H2O + SO2 3. Assign the oxidation numbers of all the elements and identify the oxidizing and reducing agents in the following redox reactions: HS" (aq) + ClO3- (aq) → S (s) + Cl(aq) (2 Pts.) Reducing agent: Oxidizing agent:

Answer 1

1. Total pressure (PT)   = 745mmHg

    vapor pressure of water (PH2O) = 23.78mmHg

partial pressure of H2 ( PH2) = Total pressure (PT) - vapor pressure of water (PH2O)

                                               = 745-23.78

                                               = 721.22mmHg

P   = 721.22/760   = 0.95atm

T = 25+273 = 298K

V   = 243ml = 0.243L

PV = nRT

n   = PV/RT

       = 0.95*0.243/(0.0821*298)

       = 0.009435moles

mass of H2 = no of moles * gram molar mass

                     = 0.009435*2

                     = 0.01887g >>>>answer

2.

H2SO3 ------------> H2O + SO2

1 mole of H2SO3 decomposes to gives 1 mole of SO2

82g of H2SO3 decomposes to gives 64g of SO2

2.20g of H2SO3 decomposes to gives = 64*2.20/82   = 1.717g of SO2 >>>>>answer

3.

H⁺S^-2^- (aq)+ Cl⁺⁵O^-23^-(aq) --------------> S⁰(s) +Cl^-(aq)

Reducing agent HS^-                                     Oxidizing agent ClO3^-