CHEM 142 FALL 2017 EXAM #4 FIRST NAME THE into HO0) 1. Hydrogen I peraxide, HuO,

Question

CHEM 142 FALL 2017 EXAM #4 FIRST NAME THE into HO0) 1. Hydrogen I peraxide, HuO, (aq) is used disinfect contact glasses. It decomposes water and oxygen gas, Oig). a) Write a balanced equation for the decomposition of HO b) How many milläiters of Os(a) at 22.0 C and 752 torr can aqueous solution containing 3 00% HO, by mass? The density iberated from 1 of the aqueous 1.01gmL 2. A 132.10 ml glass vessel weighs 56.1035g when evacuated and 562445g when filled the gaseous hydrocarbon at 749.3 mm Hg and 20.02 What is the molar mass of the gaseous with

Explanation / Answer

2H2O2 - > 2H2O + O2

Masso f 10 ml sol = 10*1.01= 10.1 gm

Mass % of H2O2= 3%

So actual masso of H2O2= .03*10.1 = 0.303 g

moles of H2O2= .303/34= 0.0089

0.0089 moles of H2O2 produce (0.0089/2) moles of O2

= .00445 moles O2

PV=nRT

V= (.00445*.082* (273+22))/(745/760)

V=0.11 lt of O2

2.

Mass of gas filled = 56.2445 - 56.1035

=0.141 g

P= 749.3 torr= (749.3/760) atm

=0.986 atm

V=132 ml =.132 l

T= 20.02 +273 K= 293.02 K

PV=nRT
n=(.986*.132)/(.082*293.02)

n=0.0054

moles = mass/MW

.0054=0.141/MW

MW= 26.11 g/mol

mol weight of gas = 26.1 g/mol

3.

Take 1 ml sol

weight of 1 ml sol = 1.209 g

1 ml water weighs= 1 gm

.209 g acid is added to 1 gm water

.209 g acid = (.209/98) moles f H3PO4

= 0.00213 moles of acid in 1 ml

=2.13 moles of acid in 1 l of water

So molarity= 2.13 M

molality = 2.13/1.2 = 1.775 m

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