Question

Sodium hydroxide, NaOH, is a strong base that is used in industrial synthesis and processes such as making paper.

What is the mass of 2.20 ×1022 molecules of NaOH (Molar mass = 40.0 g/mol)?
Express the mass in grams to three significant figures.

Answer 1

no' of molecules divide by avogadro number , 6×6.023×10^23 so (2.2×10^22)÷(6.023×10^23)
= 0.03653 moles
moles × Molar mass = mass
n×Mr=m
0.03653×40 = 1.46 grams

Answer 2

Answer:

1.46 g

Explanation:

For this exercise we need the Avogadro’s number that represents the number of molecules that has a mole of a substance and is value is 6.022x10^23. That is to say that 1 mole of NAOH has  6.022x10^23 molecules and by a rule of three we have:

1 mole NaOH ----------- 6.022x10^23 molecules

         X             ----------- 2.20x10^22 molecules

$X=\frac{(2.20x10^{22}molecules)(1moleNaOH)}{6.022x10^{23}molecules}$

X = 0.0365 moles NaOH

Then, 2.20x10^22 molecules of NaOH represent 0.0365 moles of NaOH.

To find the mass we use another rule of three with the NaOH molar mass:

1 mole NaOH             ------ 40.0 g

0.0365 moles NaOH ------ X

$X=\frac{(0.0365 moles NaOH)(40.0 g)}{1 mole NaOH}$

X= 1.46 g

So, 0.0365 moles of NaOH have a mass of 1.46 g or 2.20 ×10^22 molecules of NaOH have a mass of 1.46 g