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Chemistry, 22.06.2019 11:40
Modern pennies are composed of zinc coated with copper. a student determines the mass of a penny to be 2.482 g and then makes several scratches in the copper coaling (to expose the underlying zinc). the student puts the scratched penny in hydrochloric acid, where the following reaction occurs between the zinc and the hcl (the copper remains undissolved): zn(s) + 2 hcl(aq) → h2(g) + zncl(aq)the student collects the hydrogen produced over water at 25 °c. the collected gas occupies a volume of 0.899 l at a total pressure of 79 j mmhg. calculate the percent zinc (by mass) in the penny. (assume that all the zn in the penny dissolves.)
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Chemistry, 22.06.2019 14:00
The content of manganese (mn) in steel was determined spectrophotometrically and with the use of the standard addition method. an unknown sample of mn from a digested steel sample gave an absorbance of 0.185 when analyzed spectrophotometrically. when 5.00 ml of solution containing 95.5 ppm mn was added to 50.0 ml of the unknown steel solution (digested sample), the absorbance was 0.248. calculate the concentration, in parts-per-million (ppm), of mn in the digested steel sample solution.
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Chemistry, 22.06.2019 22:30
What relationship exists between an enzyme and a catalyst?
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Chemistry, 23.06.2019 14:00
[07.06] which of the following chemical reactions is an oxidation-reduction reaction? (2 points) wo3 + 3h2 yields w + 3h2o kno3 + licl yields lino3 + kcl caso4 + 2nacl yields na2so4 + cacl2 mg(no3)2 + 2hbr yields mgbr2 + 2hno3
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