Solid sodium metal reacts with liquid water to produce aqueous sodium hydroxide and hydrogen gas as shown by the chemical equation: 2 Na(s) +2H2O(I) —> 2 NaOH(aq) +H2(g)

How many grams of water are used in this reaction to form 4.0 g or hydrogen gas?

A) 36 g

B) 72 g

C) 80 g

D) 8 g

the answer is d. 74.02

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

c. electrical charges of ionic bonds.