IPLE CHOICE. Choose the one alternative that best completes the statement or ans

Question

IPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 1) When aqueous solutions of AgNO3 and KI are mixed, Agl precipitates. The balanced net ionic 1) A) Ag+ (aq) . NO' (aq) AgNO3 (aq) B) Ag+ (aq) + NO3-(aq) AgNO3 (s) C) AgNOg (aq) + KI (aq) Agl (aq) + KNO3 (s) D) Ag+ (aq) + r (aq) AgI (s) E) AgNO3 (aq) + Kl (aq) Agl (s) + KNO3 (aq) 2) A compound contains 40.0% C, 6.71% H, and 53.29% O by mass. The molecular weight of the compound is 60.05 amu. The molecular formula of this compound is A) CHO2 C) C2H304 D) C2H204 E) C2H402 B) CH20 3) When the following equation is balanced, the coefficients are Al(NO3)3 + Na2S A12S3 + NaNO3 A) 2, 3, 2,3 C) 2, 3,1,6 D) 4, 6,3,2 E) 2, 1,3,2 4) What mass in grams of hydrogen is produced by the reaction of 4.73 g of magnesium with 1.83 water? Mg (s) + 2H20 (l) Mg(OH)2 (s) + H2 (g) A) 0.204 B) 0.0162 C) 0.0485 D) 0.219 E 0.10 5) How many molecules of water, H0, are present n750 godt Hh01 A) 4.17 molecules B) 2.51 × 1024 molecules C) 75.0 molecules D) 5.02 × 1024 molecules E) 7.53 1024 molecules 6) The combustion of ammonia in the presence of excess oxygen yields NO2 and H20 4 NH3 (g) + 702 (g) 4NO2 (g) + 6H20 (g) The combustion of 28.8 g of ammonia consumes8of oxygen. D) 15.3 A) 28.8 B) 108 C) 54.1

Explanation / Answer

1. AgNO3(aq) + KI(aq) -----------> AgI(s) + KNO3(aq)
    Ag^+(aq) +NO3^-(aq) + K^+aq)+I^-(aq) -----------> AgI(s) + K^+(aq) +NO3^-(aq)
    removal of spectator ions to get net ionic equation
    Ag^+(aq) +I^-(aq) -----------> AgI(s)
D.Ag^+(aq) +I^-(aq) -----------> AgI(s)
2.
    Element     %      A. Wt   reltive number      simple ratio
     C          40      12       40/12 = 3.33        3.33/3.33 = 1
     H          6.71     1       6.71/1 =6.71        6.71/3.33 = 2
     O          53.29   16       53.29/16 = 3.33     3.33/3.33 = 1
        empirical formula = CH2O
           E.F.Wt          = 30g/mole
        molecular formula   = (empirical formula)n
                       n     = M.wt/E.F.Wt
                             = 60.05/30 = 2
         molecular formula    = (CH2O)2 = C2H4O2
E. C2H4O2
3.   2Al(NO3)3 + 3Na2S------> Al2S3 +6NaNO3
    C. 2 ,3,1,6
4. Mg(s) + 2H2O ------> Mg(OH)2(s) + H2(g)
    no of moles of Mg = 4.73/24 = 0.197 moles
    no of moles of H2O = 1.83/18 = 0.1016 moles
   1 mole of Mg react with 2 moles of H2O
   0.197 moles of Mg react with = 2*0.197/1   = 0.394moles of H2O
     H2O is limiting reactant
    2 moles of H2O react with Mg to gives 1 moles of H2
    0.1016 moles of H2O react with Mg to gives = 1*0.1016/2 = 0.0508 moles
     mass of H2 = 0.0508*2 = 0.1016g
E.0.1016g
5. no of moles of H2O = 75/18 = 4.17 moles
   no of molecules = no of moles *6.023*10^23
                     = 4.17*6.023*10^23 = 2.51*10^24 molecules
B. 2.51*10^24 molecules
6. 4NH3 + 5O2 --------> 4NO + 6H2O
   4moles of NH3 react with 5 moles of O2
   4*17g of NH3 react with 5*32g of O2
   28.8g of NH3 react with = 5*32*28.8/4*17   = 67.76g of O2

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