Hydrogen peroxide is used as a cleaning agent in the treatment of cuts and abras

Question

Hydrogen peroxide is used as a cleaning agent in the treatment of cuts and abrasions for several reasons. It is an oxidizing agent that can directly kill many microorganisms; it decomposes upon contact with blood, releasing elemental oxygen gas (which inhibits the growth of anaerobic microorganisms); and it foams upon contact with blood, which provides a cleansing action. In the laboratory, small quantities of hydrogen peroxide can be prepared by the action of an acid on an alkaline earth metal peroxide, such as strontium peroxide.

Explanation / Answer

SrO2(s) + 2 HCl(aq) ----> H2O2(aq) + SrCl2(aq)

As per reaction 1 mol of SrO2(s) reacts with 2 mol of HCl(aq) to form 1 mol of H2O2 (aq) and 1 mol of SrCl2(aq)

1)..

Now we are given 2.4 g Sr(OH)2 ,we find its moloes

Molar mass Sr(OH)2 = 119.62 g/mol

Moles of Sr(OH)2 = grams/molar mass = 2.4/119.62 = 0.02 moles Sr(OH)2

2)..

we are given 23.8 mL of hydrochloric acid solution containing 0.0400 g ofHCl per mL

0.04 g HCl/ml

using molar mass of HCL as 36.5 g/mol we convert it to moles per ml

0.04/36.5 = 1.096*10^-3 moles/ml

now we are given 23.8 ml as volume

so we can find moles of Hcl

as moles / volume (ml) = 1.096 *10^-3

moles = volume * 1.096 *10^-3

moles of HCl = 23.8 * 1.096 *10^-3 = 0.026 moles of HCl

3) as we see per reaction 1 mol Sr(OH)2 needs 1 mol of HCl

and 0.02 mol of Sr(OH)2 will also need 0.02 moles of HCl

but we have 0.026 moles of HCl

so moles of HCl are more than required (in excess)

so Sr(OH)2 is limiting and will be used up completely

hence 0.02 moles of Sr(OH)2 will react with only 0.02 moles of HCl( out of 0.026 moles) to form 0.02 moles of H2O2

So moles of H2O2 formed will be 0.02 moles

molar mass H2O2 = 33.996 g/mol

grams ofH2O2l = 0.02 *33.996= 0.679 g grams of H2O2(answer)

What mass of which reagent is left unreacted?
mass

mass left unreacted will be of excess reagent(HCL)

moles of HCl unreacted = 0.026-0.02 = 0.006 moles of HCL are unreacted

mass of HCl unreacted = 0.006 * 36.5 (molar mass HCl)

= 0.219 grams of HCL are unreacted (answer)

Related Questions

Navigate

• Browse (All)
• Browse H
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.