CHEM - VOLUMETRIC ANALYSIS

Scarbo

2011-07-31 12:41 am

1) What volume of hydrogenchloride, measured at s.t.p., is required to make 100 cm3 of 0.25M hydrochloric acid? ANS: 560cm32) a) What volume of water must beadded to 25cm3 of 1.0M sodium hydroxide solution to makeit 0.20M? ANS:100cm3 b)What volume of water has to be evaporate away from 50cm3 of 0.10M sodium chloride solution in order to concentrate it to 0.25M? ANS: 30 cm3 3) What volume of ammonia,measured at s.t.p., is required to neutralize 100cm3 of 0.500M sulphuric acid? ANS:2.24dm34) 8.0g of magnesium are treatedwith 100cm^3 of dilute sulphuric acid containing 196g of acid per dm3. Calculate (a) the mass of magnesiumleft (b) the volume of hydrogen produced at room conditions. ANS:a) 3.2 g b) 4.8 dm3 5) a) Hydogen peroxide solution decomposesas follows:2H2O2(aq)à 2H2O (l)+ O2(g)100cm3of a hydrogen peroxide solution are decomposed catalytically to give 480cm3oxygen at room temperature and pleasure.Assume that complete decomposition has taken place, calculate the moralityof the hydrogen peroxide solution. ANS: 0.40M b)Acidified potassium permanganate solution oxidizes oxalic (ethanedioic) acid to carbon carbon dioxide and water.2MnO4-(aq) + 5H2C2O4(aq)+6H+(aq)à 2Mn2+(aq)+10CO2(g)+8H2O(l) 25cm3 of . 20 M oxalic acid solution required 20 cm3 ofacidified potassium permanganate solution for complete reaction. Find the morality ofthe potassium permanganate solution. ANS: 0.10M THANKS!!

回答 (1)

己式庚辛

2011-07-31 4:34 am

✔ 最佳答案

1.
first, find the no. of mole of HCl in the acid:
no. of mole = volume (in dm^3) x molarity (in M).

then, 1 mole of gas at stp occupies 22.4 dm^3 of volume.

2.
two methods.
A: from molarity and volume, calculate no. of mole of NaOH in undiluted solution.

then, since no. of mole of solute doesn't change, you can back calculate the new volume from no. of mole and new molarity:
new volume = no. of mole / molarity

volume change = new volume - old volume

B: remember,
c1V1 = c2V2
c is concentration (in whatever unit), V is volume (in whatever unit);
1 & 2 are before & after procedures of dilution/concentration.

3.
first write reaction equation, find the mole ratio of NH3 and H2SO4.
then, no. of mole of H2SO4 = volume x molarity

from mole ratio, find no. of mole of NH3; follow Q.1's approach.

4.
a. find molar mass of H2SO4 = 98.1 g/mol
then, find mass of H2SO4 in 100ml acid
then, no. of mole of H2SO4 = mass / molar mass

write equation, find mole ratio between H2SO4 & Mg
find original no. of mole of Mg
find no. of mole of Mg reacted
find no. of mole of Mg unreacted
find mass of Mg unreacted = no . of mole x molar mass of Mg

b. from equation, find no. of mole of H2 produced
from no. of mole, find volume according to Q.1

5.
spell "pressure" and "molarity".

find no. of mole of O2 produced = volume / molar volume at rtp
according to mole ratio, find no. of mole of H2O2 present
with no. of mole & volume, find molarity isn't difficult.

2011-08-08 18:11:59 補充：
what do you want?
do you want every single detailed steps done for you?
not to question whether you're copying for homework, the guides should be enough for average students to follow the sequence of solving / answering these questions!

👍 0 👎 0