Please help!!! the concentration of the stock solution? (with steps please)
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Please help!!! the concentration of the stock solution? (with steps please)

[From: ] [author: ] [Date: 11-05-22] [Hit: ]
The chemist then takes four 250 mL volumetric flasks to prepare the standard solutions. 1 mL, 2 mL, 5 mL and 10 mL of stock are pipetted into these four flasks, and the volume made up with water.The concentrations of these four flasks are.......
A chemist in a water treatment plant requires five solutions of NaOH – a stock solution and four standard solutions.

40.00 g of NaOH are dissolved in water in a 250 mL volumetric flask to prepare the stock solution.

What is the concentration in moles/litre of the stock solution? Fill in the Blank 01 M

The chemist then takes four 250 mL volumetric flasks to prepare the standard solutions. 1 mL, 2 mL, 5 mL and 10 mL of stock are pipetted into these four flasks, and the volume made up with water.

The concentrations of these four flasks are..?


(Atomic Masses; Na = 23.0, O = 16.0, H = 1.00)

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1) The atomic mass of NaOH is 23.0 + 16.0 + 1.00 = 40.0g/mol

The moles of dissolved NaOH is 40.00g of NaOH * 1mol/40g = 1 mol NaOH

1 mol of NaOH is dissolved in 250 mL water, which gives a concentration of 1mol/0.25L = 4mol/L = 4 M

2) 1mL of 4M NaOH = 0.001 L * 4mol/L = 0.004 mol NaOH is present. If the volume is diluted from 1 mL to 250 mL, the resulting concentration would be 0.004mol/0.250L = 0.016 M NaOH

The same procedure for the next three.

2mL of 4M NaOH = 0.002 L * 4mol/L = 0.008 mol NaOH is present. If the volume is diluted from 1 mL to 250 mL, the resulting concentration would be 0.008mol/0.250L = 0.032 M NaOH

5mL of 4M NaOH = 0.005 L * 4mol/L = 0.020 mol NaOH is present. If the volume is diluted from 1 mL to 250 mL, the resulting concentration would be 0.020 mol/0.250L = 0.080 M NaOH

10mL of 4M NaOH = 0.010 L * 4mol/L = 0.040 mol NaOH is present. If the volume is diluted from 1 mL to 250 mL, the resulting concentration would be 0.040mol/0.250L = 0.160 M NaOH

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Standard # 1 : 1 ml of stock in 250 ml water =4 ml of 1 M solution in a liter. So this is 0.004 M
Standard # 2: 2 ml of stock in 250 ml water = 8 ml of 1M solution in a liter. So this is 0.008 M
Standard # 3: 5 ml of stock in 250 ml water = 20 ml of 1M solution in a liter. So this is 0.020 M
Standard # 4: 10 ml of stock in 250 ml water= 40 ml of i M solution in a liter. So this is 0.040 M NaOH solution.
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