Question

How many grams of Na2CO3 must be dissolved into 155g of water to create a solution with a molarity of 8.20 mol/kg

Answer 1

Answer:

135g Na2CO3

Explanation:

I'm going to assume you mean Molality which is mol solute/kg solvent

Molarity would be mol soute/ L solution

we know we have 155g of water which is .155 kg

essentially we have the equation:

mol/kg = 8.20

we substitute .155 in for kg and get:

mol/.155 = 8.20

Solving this  gives mol = 1.271

now we must convert to grams using the molar mass

Molar mass Na2CO3 = 106G/mol

so to cancel moles we multiply:

1.271mol x 106g/mol

= 135g

Answer 2

The mass of $Na_2CO_3$ will be 135 grams.

What is Molarity?

It is defined as ratio of number of moles over the volume of the solution.

Molarity= n / V

Given:

Mass of water= 155g or 0.155 kg

Molarity = 8.20 mol / kg

On solving

Number of moles = 1.271 moles

Molar mass  $Na_2CO_3$= 106 g/mol

Calculation for mass:

Mass = number of moles * Molar mass

Mass = 1.271mol * 106g/mol

Mass = 135g

Find more information about Molarity here:
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