BACE Molar Solutions

Molarity and
Molar Solutions
BACE Prep

The Mole

1 mole is equal to 6.02 x 10^23 particles of a substance

1 mole is also equal to the molecular weight of a compound, expressed in grams

The Mole

1 mole of carbon atoms weighs 12g

The Mole

1 mole of water weighs
(1 x 2) + 16 = 18g

Math Response

What is the mass of one mole of methane, CH4. (Use whole numbers.)

Type answer here

Correct Answer: 16

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Rad

Math Response

What is the mass of one mole of glucose? (Use whole numbers.)

Type answer here

Correct Answer: 180

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Rad

Multiple Choice

What is the mass of 5 moles of sodium chloride? (Use two decimal places.)

• 292.25

• 58.45

• 6.02

• 5

Molarity

Molarity indicates the moles of a substance per liter of solution.

A 1M sol'n has one mole per liter.
A 5M sol'n has 5 moles per liter.

Math Response

How many grams of glycine are needed to make a 2M aqueous glycine solution? (Use whole numbers.)

Type answer here

Correct Answer: 150

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Rad

Math Response

The MW of Magnesium Chloride is 95.21 Da. How much MgCl2 is needed to make 2L of a 1M solution? (Use two decimal places.)

Type answer here

Correct Answer: 190.42

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Multiple Choice

The MW of glycine is 75 Da and the MW of glucose is 190 Da. You have a 1M sol'n of glycine and a 1M sol'n of glucose. How do the number of moles of glucose and glycine compare?

• same # of moles of glycine and glucose

• more moles of glucose

• more moles of glycine

Multiple Choice

The MW of glycine is 75 Da and the MW of glucose is 190 Da. You have a 1M sol'n of glycine and a 1M sol'n of glucose. How do the number of grams of glucose and glycine compare?

• same # of grams of glycine and glucose

• more grams of glucose

• more grams of glycine

​Solution Preparation

Use conversion factors to calculate the amount of solute(s) you will need.
Dissolve the substance(s) in about 70% of the water. Adjust pH, if needed. Then bring the final volume to the desired volume by adding more water.
Use the most accurate tools available, typically graduated cyliners or volumetric flasks.

100mL x (1L/1000mL) x (58.44g/1mol) x (5mol/1L) = 29.29g NaCl

Dissolve in some water (70-80mL?) and raise the volume to 100mL.

How would you prepare 100mL of a 5M NaCl solution?

MW of NaCl is 58.44 Da

Sample Problem

Math Response

The MW of glucose is 180 Da. How many grams of glucose would you need to make 400mL of a 0.36M solution? (Use 2 decimal places.)

Type answer here

Correct Answer: 25.92

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Rad