Given this equation. C3H8 + 5O2 -> CO2 + H2O.

How many moles of O2 will be needed to comepletely burn 1.75 moles of propane C3H8?

First, balance the equation.

C3H8 + 5O2 -> 3CO2 +4H2O.

Use the coefficients to convert mols propane to mols O2 this way.
1.75 mols C3H8 x (5 mols O2/1 mol C3H8) = 1.75 x 5/1 = ?

To find out how many moles of O2 are needed to completely burn 1.75 moles of C3H8 (propane), we need to use the balanced chemical equation.

The balanced equation is: C3H8 + 5O2 -> 3CO2 + 4H2O.

According to the equation, for every 1 mole of C3H8, we need 5 moles of O2. Therefore, we can use a ratio to find out how many moles of O2 are needed for 1.75 moles of C3H8.

1.75 moles C3H8 * (5 moles O2 / 1 mole C3H8) = 8.75 moles O2.

Therefore, 8.75 moles of O2 will be needed to completely burn 1.75 moles of C3H8.

To determine how many moles of O2 are needed to completely burn 1.75 moles of propane, we need to use the balanced chemical equation for the combustion of propane.

The balanced chemical equation is:
C3H8 + 5O2 -> 3CO2 + 4H2O

From the equation, we can see that for every 1 mole of C3H8, we need 5 moles of O2 to react. Therefore, we can set up a proportion to find out how many moles of O2 are needed for 1.75 moles of C3H8.

1 mole C3H8 / 5 moles O2 = 1.75 moles C3H8 / x moles O2

Cross-multiplying, we have:
1 * x = 5 * 1.75
x = 8.75

So, 8.75 moles of O2 will be needed to completely burn 1.75 moles of propane C3H8.