[tex]Molar{Mass} H_{2}O_{2} =2*16.0+2*1.0= 34.0 g/mol
42.0 g H_{2}O_{2}* \frac{1 mol H_{2}O_{2}}{34.0 g H_{2}O_{2}} = 1.24 mol H_{2}O_{2}
2H_{2}O_{2} --\ \textgreater \ 2 H_{2}O +O_{2}
\\2 mol ----2 mol (from// reaction)
\\1.24 mol ---1.24 mol (from the problem)
Answer: 1.24 mol H_{2}O.[/tex]
