:at a certain temperature this reaction follows first-order kinetics with a rate constant of 0.00771 nh, oh(aq) - nh, (aq) +h,0(aq) suppose a vessel contains nh oh at a concentration of 1.42 m. calculate how long it takes for the concentration of nh oh to decrease to 17.0% of its initial value. you may assume no other reaction is important round your answer to 2 significant digits. x 5 ?

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 answers are

c and c