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3 years ago

To be effective, a certain drug must not drop below 15 mg in the body. A 120

1 answer:

6 0

Thus, it follows that after 4 to 5 half-lives, the plasma concentrations of a given drug will be below a clinically relevant concentration and thus will be considered eliminated. Conversely, the accumulation of a drug can reach a steady-state during an infusion

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The thin outer layer of Earth, called the crust, contains only 0.50 percent of Earth's total mass and yet is the source of almos

Rzqust [24]

Answer:

The mass of silicon in kilograms in Earth's crust is $7.2729\times 10^{21} kg$ .

Explanation:

Mass of Earth = $5.9\times 10^{21} tons$

(1 ton= 2000 lb)

(1 lb =453.6 g)

1 ton = 2000 × 453.6 g =907,200 g

Mass of Earth = $5.9\times 10^{21}\times 907,200 g=5.3524\times 10^{27} g$

Percentage of earth crust = 0.50%

Mass of earth crust = M

$0.50\%=\frac{M}{5.3524\times 10^{27}}\times 100$

$M=2.6762\times 10^{25} g$

Percentage of the silicon in Earth's crust = 27.2 %

Mass of silicon in in Earth's crust = m

$Si\%=\frac{m}{M}\times 100$

$27.2\%=\frac{m}{2.6762\times 10^{25} g}\times 100$

$m = 7.2792\times 10^{24} g=7.2729\times 10^{21} kg$

1000 g = 1 kg

The mass of silicon in kilograms in Earth's crust is $7.2729\times 10^{21} kg$ .

7 0

3 years ago

Suppose that a certain biologically important reaction is quite slow at physiological temperature (37 oC) in the absence of a ca

Oksi-84 [34.3K]

Answer:

30 kJ

Explanation:

Arrhenius equation is given by:

$k=Aexp(-Ea/RT)\\$

Here, k is rate constant, A is Pre-exponential factor, Ea is activation energy and T is temperature.

taking natural log of both side

ln k = ln A - Ea/RT

In Arrhenius equation, A, R and T are constant.

Therefore,

$ln\frac{k_2}{k_1} =\frac{Ea_1-Ea_2}{RT}$

$Ea_1-Ea_2$ is the lowering in activation energy by enzyme,

R = 8.314 J/mol.K

T = 37°C + 273.15 = 310 K

$\frac{k_2}{k_1} =1\times 10^5$

$ln 1\times 10^5 =\frac{Ea_1-Ea_2}{RT}\\{Ea_1-Ea_2} = 11.512 \times 8.314 \times 310\\=29670\ J\\=30\ kJ$

4 0

3 years ago

What is the identity of the element, and how many neutrons does it have? An elements most stable ion forms an ionic compound wit

Pani-rosa [81]

Answer:

B. CA, 14

Explanation:

Atoms of elements contain small particles known as electrons, neutrons, and protons. The nucleus of an atom is made up of neutrons and protons which are at the center of the atom. Electrons on the other hand surrounds the nucleus. Electron has negative charge while proton has a positive charge. The number of neutrons is equivalent to the number of protons . In addition, the number of protons is equal to mass number minus the number of electrons.

For the compound $XCl_{2}$ , it can be broken down into $X^{2+}$ and $2Cl^{-}$ . Its ion has a mass of 34 and 18 electrons which means it has already lost 2 electrons.