Mga lisod answeran

Question 1

One ml of a bacterial culture was pipetted into a 9 ml dilution
blank. One-tenth ml of this dilution was pipetted into a 9.9 ml
dilution blank. From this dilution, one-tenth ml was plated with 25 ml of culture medium. 220 colonies arose after incubation. How many
colony-forming units were present per ml of the original culture?

a. 2.2 x 10^6
b. 2.2 x 10^5
c. 2.2 x 10^4
d. 2.2 x 10^7

Answer 1

a. 2.2 x 10^6

Question 2

Calculate the difference in calories between G and A at 25C for
the reaction:

H2 (g, 1atm) + 1/2 O2 (g, 1 atm)  H2O(l)

a. –256 cal
b. –888 cal
c. –904 cal
d. –1058 cal

Answer 2

b. –888 cal

Question 3

A 0.7121 g sample of wheat flour was analyzed by the Kjeldahl
method. The ammonia formed by addition of concentrated base after
digestion with H2SO4 was distilled into 25.00 mL of 0.04977 M HCl.
The excess HCl was then back titrated with 3.97 mL of 0.04012 M
NaOH. Calculate the percent protein in the flour (f = 5.70)

a) 12.16%
b)24.32%
c)12.79
d)6.40%

Answer 3

a) 12.16%

Question 4

A 0.8040-g sample of an iron ore is dissolved in acid. The iron is
then reduced to Fe+2 and titrated with 47.22 mL of 0.02242 M KMnO4
(158.04g/mol) solution. Calculate the results of this analysis in
terms of %Fe (55.847g/mol).

a) 22.06%
b)36.77%
c)14.71%
d)44.12%

Answer 4

b)36.77%

Question 5

The Philippine cornstarch Corporation prepares pharmaceutical
glucose from cornstarch by enzyme hydrolysis. It was observed that
when the starch concentration of the slurry was 5%, the rate of conversion of starch to glucose was 0.04 kg/s. When the starch
concentration was made 10%, the turnover rate was 0.07 kg/s. The maximum production level of glucose that can reasonably be attained
per shift of 8 hours is

a. 6084 kg
b. 8064 kg
c. 1008 kg
d. 0.28 kg

Answer 5

b. 8064 kg

Question 6

A certain quantity of nitrogen gas collected over water at 20C and
at a total pressure of 745 mm Hg has a volume of 200 mL. What will be
the volume of the nitrogen in a completely dry state at 780 mm Hg pressure and at 48C. The vapor pressure of water at 20C is 17.54 mm
Hg.

a) 211.45 mL
b) 209.27 mL
c) 206.75 mL
d) 204.34 mL

Answer 6

d) 204.34 mL

Question 7

A base mixture sample weighing 976 mg was dissolved in sufficient
water to make 100 mL solution and divided into two equal portions. The
first portion was titrated with 52.05 mL of 0.1004M HCl to the methyl
red end point. The other portion was titrated with 23.02 mL of the acid to the phenolphthalein endpoint. Calculate the % composition of
sample.
a) 50.16% NaHCO3, 50.20% Na2CO3
b) 10.38% NaHCO3, 50.20% Na2CO3
c)23.90% NaHCO3, 50.20% Na2CO3
d)18.94% NaHCO3, 62.70% Na2CO3

Answer 7

b) 10.38% NaHCO3, 50.20% Na2CO3

Question 8

The phosphate in a 3000 mg sample of industrial detergent was
precipitated by the addition of 1 gram AgNO3. The solution was filtered
and the filtrate required 18.23 mL of 0.1377 M KSCN. Calculate the
percentage of phosphate in the detergent. AgNO3 (169.87 g/mol) PO4–3
(94.97 g/mol)
a)3.56% b) 7.12% c) 5.35% d) 10.69%