9.69×10^25 formula units of iron(iii) nitrate is equal to how many moles of fe(no3)3?

160.9 mol ≅ 161.0 mol.

Explanation:

Using cross multiplication:

1.0 mole of Fe(NO₃)₃ contains → 6.022 x 10²³ formula units.

??? mole of Fe(NO₃)₃ contains → 9.69 x 10²⁵ formula units.

∴ The no. of moles of He contains (9.69 x 10²⁵ formula units) = (1.0 mol)(9.69 x 10²⁵ formula units.)/(6.022 x 10²³ formula units) = 160.9 mol ≅ 161.0 mol.

in scientific notation, the value of the  speed of light in a vacuum

  will be written as 2.995 * 10^8. when this value is represented in the form of

  a * 10^b, then, a = 2.995 and b = 8.

the value of the speed of light in a vacuum given above can also be rounded up to approximately 300000000. in this case, the scientific notation will be written as 3 *10^8.