Question

20 microliters of 1% H2O2 (weight by volume) was added to 2980 microliters of water to make 3000 microliters of solution.

(a) What is the concentration of H2O2 for this scenario?

(b) What is the concentration of H2O2 if 60 microliters of 1% H2O2 was added to 2940 microliters water?

(c) What is the concentration of H2O2 if 100 microliters of 1% H2O2 was added to 2900 microliters water?

Please show your work so I can replicate them in other similar situations, thank you.

Answer 1

Answer – a) Given, 20 μL 1% H₂O₂ (weight by volume)

Volume of water = 2980 μL ,

1% H₂O₂ weight by volume in 20 μL means

1 g of H₂O₂ in 100 mL

We know, 1 μL = 0.001 mL

So, 20 μL = ?

=0.020 mL

So, 100 mL = 1.0 g

0.020 mL = ?

= 0.0002 g of H₂O₂

So moles of H₂O₂ = 0.0002 g /34.014 g.mol^-1

                              = 5.88*10^-6 moles

Total volume 3000 μL

We know

1 μL = 1.0*10^-6 L

So, 3000 μL = ?

= 0.003 L

So, [H₂O₂] = 5.88*10^-6 moles / 0.003 L

                   = 0.00196 M

b) 60 microliters of 1% H2O2 , volume of water = 2940 microliters

1% H₂O₂ weight by volume in 60 μL means

1 g of H₂O₂ in 100 mL

We know, 1 μL = 0.001 mL

So, 60 μL = ?

=0.060 mL

So, 100 mL = 1.0 g

0.060 mL = ?

= 0.0006 g of H₂O₂

So moles of H₂O₂ = 0.0006 g /34.014 g.mol^-1

                              = 1.76*10^-5 moles

Total volume = 2940 +60 = 3000 μL

We know

1 μL = 1.0*10^-6 L

So, 3000 μL = ?

= 0.003 L

So, [H₂O₂] = 1.76*10^-5 moles / 0.003 L

                   = 0.00588 M

c) 100 microliters of 1% H2O2 , volume of water = 2900 microliters

1% H₂O₂ weight by volume in 1000 μL means

1 g of H₂O₂ in 100 mL

We know, 1 μL = 0.001 mL

So, 100 μL = ?

=0.1 mL

So, 100 mL = 1.0 g

0.10 mL = ?

= 0.001 g of H₂O₂

So moles of H₂O₂ = 0.001 g /34.014 g.mol^-1

                              = 2.94*10^-5 moles

Total volume = 2900 +100 = 3000 μL

We know

1 μL = 1.0*10^-6 L

So, 3000 μL = ?

= 0.003 L

So, [H₂O₂] = 2.94*10^-5 moles / 0.003 L

                   = 0.00980 M