Question

Question 4-6 are one question but just with different answers answer the question

Answer 1

Step 1 - Understanding how to discover the relation in moles

Let's first take a closer look at the given equation:

`3\text{MnO}_(2(s))+4Al_((s))\to3Mn_((s))+2Al_2O_(6(s))`

In this equation, we can see there are both bigger numbers before the formula of the substances and smaller ones, bellow them. They mean different things:

I. Bigger numbers: They indicate the proportion of each substance in number of moles. In this equation, for example, we know that 3 moles of MnO2 react with 4 moles of Al, thus producing 3 moles of Mn and 2 moles of Al2O6.

II. Smaller numbers: They are just part of the formula of the substance. They indicate how many atoms of each type there are in the molecule. In ionic substances, they also indicate proportion, but always within the substance. We do not use them to discover how many moles do we need of certain reactant of product.

Step 2 - Using the bigger numbers to answer the exercise

4) Note, by the reaction in step 1, that 3 moles of MnO2 react with 4 moles of Al, producing 2 moles of Al2O6. Therefore, whenever we use 3 moles of MnO2, we will produce 2 moles of Al2O6.

5) Note that 4 moles of Al produce 2 moles of Al2O6. This is always a fixed proportion. We can set thus the following relation:

`\begin{gathered} 4\text{ moles of Al produce}----\text{ 2 moles of Al2O6} \\ 2\text{ moles of Al would produce -- x} \\ \\ x=(2*2)/(4)=1 \end{gathered}`

6) Note that 3 moles of MnO2 produce 2 moles of Al2O6. This is always a fixed proportion. We can set thus the following relation:

`\begin{gathered} 3\text{ moles of MnO2 produce ---- 2 moles of Al2O6} \\ x\text{ moles would produce ------ 3 moles of Al2O6} \\ \\ x=(3*3)/(2)=4.5 \end{gathered}`

It would be needed thus 4.5 moles of MnO2.