How many grams of cu2s could be produced from 9.90 g of cucl with an excess of h2s gas?

 The  grams   of CuS  produced is  7.95  mass

  calculation

Step  1:  write  the equation  for  reaction

2CUCl  +H2S → CU2S  + 2 HCl

Step 2 :  calculate  the moles of  CUCl

moles=  mass/molar mass

The  molar  mass of CuCl = 63.5 for CU +35.5  for Cl  =99 g/mol

 =9 .90 g  /  99  g/mol= 0.1  moles

Step 3:  use  the mole ratio to determine the moles  of CU2S

CUCl:CU2S  is  2:1 therefore  the  moles of CU2S =0.1  x1/2=0.05 moles

step 4:  find  the  mass of CU2S

mass=  molar mass  x  moles

The  molar mass  of CU2S  = (2 x 63.5) +  32 =159 g/mol

 mass =  0.05   x 159= 7.95   mass

answer:

technetium is the most reactive. this is followed by silver. the least reactive out of these three elements is strontium.