How many grams are there in 9.4 x1023 molecules of h2?

In order to solve this, it is recommended that you use stoichiometry. You need to use the mole hill and go from molecules to moles to grams. In order to go from molecules to moles, you must use Avogadro's number (6.02x10^23). Next, you need to go from moles to grams using atomic mass (I usually just go out to two decimal places). So, your atomic mass should be around 2.02g for H2. Your final answer should be around 3.1g H2 (don't forget  significant figures!). Hope this helped

the ratio of the conjugate base to the acid required to attain the desired ph.

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