Today, there are about how many people living on the earth?
3.4 billion
7.5 billion
9.0 billion
6.6 billion

The correct answer is option B, 7.5 billion

Explanation:

As per the US Census Bureau, the world population in year 2016 was approximately US  

7346235000. As per the UN estimate there were 7 billion people on planet earth in 2011 and World Bank estimates say that there were 7 billion people in year 2012

The top most populated countries in coming year (along with their population) would be  

China                            1,367,485,388

India                            1,251,695,584

United States                    321,368,864

l dont know l am s sorry

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