The gas phase decomposition of hydrogen peroxide at 400 °C H2O2(g)H2O(g) + ½ O2(g)

is second order in H2O2 with a rate constant of 0.650 M-1 s-1.

If the initial concentration of H2O2 is 8.00×10-2 M, the concentration of H2O2 will be 1.70×10-2 M after
seconds have passed.

your answer is c) plasma

~*"auba14"*~

as given the equation is

2al + 6 hcl > 2 alcl3 + 3 h2(g)

as per equation two moles of aluminum reacts with six moles of hcl to give two moles of alcl3 and three moles of hydrogen gas

given: three moles of al are present and 7 moles of hcl

for three moles of aluminum nine moles of hcl will be required

however as 7 moles of hcl are present so the limiting reagent is hcl

hcl is going to decide the number of moles of product formed

when six moles of hcl are present = 3 moles of h2 are formed

when one mole of hcl is present == 3/6 mole sof h2 will be formed

when 7 moles of hcl are present = 3 x 7/ 6 moles of h2 will be formed = 3.5 moles of h2

the answer is symmetrical : )