Number of molecules = moles x Avogadro's number = 2 moles x 6.022 x 10^23 molecules/mole = 1.2044 x 10^24 molecules.

Molar mass of NaOH = 23 + 16 + 1 = 40 g/mol. Number of moles = mass/molar mass = 100 g / 40 g/mol = 2.5 moles.

Molar mass of O2 = 16*2 = 32 g/mol. Number of moles = mass/molar mass = 32g/32g/mol = 1 mole.

Moles = Molarity * Volume (L) = 0.2 M * 0.5 L = 0.1 moles.

The d-subshell has 5 orbitals.

The p subshell has 3 orbitals (px, py, pz).

The number of ways to select 2 boys from 5 is C(5, 2) and 2 girls from 5 is C(5, 2). Total = C(5, 2) * C(5, 2) = 10 * 10 = 100.

The number of ways is 5C2 * 6C3 = 10 * 20 = 200.

The number of ways is 5C2 * 7C3 = 10 * 35 = 350.

The number of ways is 8C2 * 6C3 = 28 * 20 = 560.

The number of ways to select 2 boys from 5 is 5C2 and 3 girls from 7 is 7C3. Total = 5C2 * 7C3 = 10 * 35 = 350.

The number of ways to choose 2 from 5 is C(5,2) = 10.

The number of ways to select 2 students from 5 is given by 5C2 = 10.

The number of ways to select 2 from 8 is C(8, 2) = 28.

The number of ways to select 3 books from 10 is given by 10C3 = 120.

The number of ways to arrange 5 people is 5! = 120.

The number of ways to choose 3 from 7 is C(7, 3) = 35.

The number of arrangements of 3 distinct balls is 3! = 6.

Each gift can go to any of the 5 children, so the total ways = 5^3 = 125.

The number of ways to award 3 trophies to 5 students is given by P(5,3) = 5! / (5-3)! = 60.

The number of ways to choose 3 balls from 8 is given by 8C3 = 56.

The number of ways to award 3 prizes is P(10, 3) = 720.

The number of arrangements is 5! / (3! * 2!) = 10.

The number of ways to select 3 students from 10 is given by 10C3 = 120.

The number of arrangements of 4 distinct flags is 4! = 24.

The number of ways to choose 4 fruits from 6 is C(6, 4) = 15.

The number of ways to choose 4 fruits from 8 is given by 8C4 = 70.

The number of ways to select 4 fruits from 8 is given by 8C4 = 70.

The number of ways is 8C4 = 70.

The number of ways to choose 4 letters from 11 is 11C4 = 330.