A4 g sample of sodium hydroxide, naoh, is dissolved in water and made up to 500 cm3 of aqueous solution. what is the concentration of the resulting solution?

0.2 M  is the concentration of the resulting solution

Explanation:

M is a unit for concentration which means mole of solute in 1L of solution.

According to the received information, we have 4 g in 500 mL of solution.

In 0.5L we have 4 g of solute

In 1L we have (1 .4)/0.5 = 8 g of solute

Let's convert the mass in mole

Mass / Molar mass = Mole

Molar mass NaOH = 40 g/m

8g / 40 g/m = 0.2M

Concentration in molarity is 2 M.

Explanation:

Mass of NaOH dissolved = 4 g

Molar mass of NaOH = 40 g/mol

Number of moles =

Concentration is usually expressed in terms of molarity.

Molarity is defined as number of moles of solute per litre of solution.

Molarity =

              =

Hence concentration of the solution is 2 M.

n2(g) + 3h2-> 2nh3(g)   this is the balanced equation

note the mole ratio between n2, h2 and nh3.   it is 1 : 3 : 2   this will be important.

moles n2 present = 28.0 g n2 x 1 mole n2/28 g = 1 mole n2 present

moles h2 present = 25.0 g h2 x 1 mole h2/2 g = 12.5 moles h2 present

based on mole ratio, n2 is limiting in this situation because there is more than enough h2 but not enough n2.

moles nh3 that can be produced = 1 mole n2 x 2 moles nh3/mole n2 = 2 moles nh3 can be produced

grams of nh3 that can be produced = 2 moles nh3 x 17 g/mole = 34 grams of nh3 can be produced

note:   the key to this problem is recognizing that n2 is limiting, and therefore limits how much nh3 can be produced.