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Ad libitum [116K]
3 years ago
8

A certain drug has a half-life in the body of 4.0h. What should the interval between doses be, if the concentration of drug in t

he body should not fall below 15.% of its initial concentration? Round your answer to 2 significant digits.
Chemistry
1 answer:
scZoUnD [109]3 years ago
8 0

Answer:

Explanation:

half life = 4 h

initial concentration = 100

final concentration = 15

Time = t

No of half life  x = t / 4

15 = 100 x ( 1/2 )ˣ

.15 =  ( 1/2 )ˣ

ln .15 = - x ln2

x = - ln .15 / ln 2

= 1.897 / .693

x = 2.737

x = t / 4

t = 2.737 x 4 = 11 h approx .

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Explanation:

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3 years ago
A gas mixture at 535.0°C and 109 kPa absolute enters a heat exchanger at a rate of 67.0 m3/hr. The gas leaves the heat exchanger
SVEN [57.7K]

Answer:

the heat rate required to cool down the gas from 535°C until 215°C is -2.5 kW.

Explanation:

assuming ideal gas behaviour:

PV=nRT

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R = 0.082 atm L /mol K

n = PV/RT = 109 Kpa = 1.07575 atm * 18.611 L/s /(0.082 atm L/mol K * 488 K)

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3 years ago
Why atomic mass is an average vàlue​
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Answer:

The atomic mass is the average number of protons and neutrons for all natural isotopes of an element. It is a decimal number.

Explanation:

Atomic Mass and Mass Number Example :

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1H has 1 proton. Its mass number is 1. 2H has 1 proton and 1 neutron. Its mass number is 2. 3H has 1 proton and 2 neutrons. Its mass number is 3. 99.98% of all hydrogen is 1H 0.018% of all hydrogen is 2H 0.002% of all hydrogen is 3H Together, they give a value of atomic mass of hydrogen equal to 1.0079 g/mol.

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3 years ago
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We have that the  the molarity of methanol in the solution is mathematically given as

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<h3>Chemical Reaction</h3>

Question Parameters:

An <u>aqueous </u><em>solution </em>of methanol (MM = 32.04 g/mol)

A molality of 8.83 m and a density of 1.15 g/mL.

Generally the equation for the   is mathematically given as

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