Given:
- Number of moles of metal M = 0.7 moles
- Metal M reacts completely with an excess of fluorine to form 45g of MF2

To Find:
- Number of moles of fluorine (F) present in MF2

Explanation:
To determine the number of moles of fluorine present in MF2, we need to use the given information and perform the following steps:

Step 1: Determine the molar mass of MF2:
- Given that 45g of MF2 is formed, we need to determine the molar mass of MF2 to convert the mass to moles.
- The molar mass of an element is the sum of the atomic masses of all the atoms present in its chemical formula.
- The atomic mass of fluorine (F) is approximately 19 g/mol, and the atomic mass of metal M is unknown.
- The molar mass of MF2 can be calculated as follows:
- Molar mass of MF2 = Molar mass of M + 2 * molar mass of F

Step 2: Calculate the molar mass of metal M:
- Rearranging the formula for molar mass of MF2, we have:
- Molar mass of M = (Molar mass of MF2) - 2 * (molar mass of F)

Step 3: Determine the number of moles of F:
- To calculate the number of moles of F, we can use the given mass of MF2 and the molar mass of F.
- The number of moles (n) can be calculated using the formula:
- n = (mass of substance) / (molar mass of substance)

Step 4: Substitute the values into the formula:
- Substitute the values into the formula for the number of moles of F:
- n = 45g / (molar mass of F)

Step 5: Calculate the molar mass of MF2:
- Substitute the molar mass of F and the calculated molar mass of metal M into the formula for molar mass of MF2:
- Molar mass of MF2 = (molar mass of M) + 2 * (molar mass of F)

Step 6: Calculate the number of moles of F:
- Substitute the values into the formula for the number of moles of F:
- n = 45g / (molar mass of MF2)

Step 7: Calculate the number of moles of F:
- Calculate the number of moles of F by multiplying the calculated moles of F by the stoichiometric coefficient in the balanced chemical equation.

Summary:
- By following the steps outlined above, we can determine the number of moles of fluorine (F) present in MF2. This calculation involves determining the molar mass of MF2, calculating the molar mass of metal M, and then using the given mass of MF2 to calculate the number of moles of F.