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Calculate the molarity of a solution that contains 1.37 grams NaOH dissolved in enough
water to make 150 mL of solution.
Select one:
O a. 0.228 M
O b. 0.395 M
O c. 9.13 M
O d. 0.0633 M
O e. 1.00 M


Sagot :

Answer:

a. 0.228 M

Explanation:

Molarity is a concentration unit, and is defined as the number of moles per litre of solution.

To convert grams into number of moles, divide the mass by the relative molecular mass (Mr) of the compound. The Mr of NaOH can be calculated by taking the sum of the relative atomic masses of Na, O and H with the help of a periodic table.

Mr of NaOH

= 23 +16 +1

= 40

Number of moles of NaOH

= 1.37 ÷40

= 0.03425 moles

Convert the volume of solution into litres:

150mL

= (150 ÷1000) L

= 0.15 L

This means that 0.15L of solution contains 0.03425 moles of NaOH. Molarity is looking at the number of moles for every 1L of solution, thus divide the number of moles by the volume in litres to find the solution's molarity.

Molarity of solution

= 0.03425 ÷0.15

= 0.22833 (5 s.f.)

= 0.228 M (3 s.f.)

Thus, option a is correct.

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