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aliina [53]
3 years ago
13

g Phosphorus -32 is a commonly used radioactive nuclide in biochemical research, particularly in studies of nucleic acids. The h

alf-life of phosphorus-32 is 14.3 days. What mass of phosphorus-32 is left from an original sample of 175 mg of Na332PO4 after 35.0 days
Chemistry
1 answer:
Setler79 [48]3 years ago
3 0

Answer:

6.88 mg

Explanation:

Step 1: Calculate the mass of ³²P in 175 mg of Na₃³²PO₄

The mass ratio of Na₃³²PO₄ to ³²P is 148.91:31.97.

175 mg g Na₃³²PO₄ × 31.97 g ³²P/148.91 g Na₃³²PO₄ = 37.6 mg ³²P

Step 2: Calculate the rate constant for the decay of ³²P

The half-life (t1/2) is 14.3 days. We can calculate k using the following expression.

k = ln2/ t1/2 = ln2 / 14.3 d = 0.0485 d⁻¹

Step 3: Calculate the amount of P, given the initial amount (P₀) is 37.6 mg and the time elapsed (t) is 35.0 days

For first-order kinetics, we will use the following expression.

ln P = ln P₀ - k × t

ln P = ln 37.6 mg - 0.0485 d⁻¹ × 35.0 d

P = 6.88 mg

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6. The Earth’s electric field is directed vertically downward; at the ground level its strength is E = 130 N/C, and at an altitu
Alexxx [7]

Answer:

5.31x10⁻⁶ C

Explanation:

The cube is located 100 m altitude from the ground, so the superior face is at 100m and has E = 70 N/C, and the inferior face is at the ground with E = 130 N/C.

The electric field is perpendicular to the bottom and the top of the cube, so the total flux is the flux at the superior face plus the flux at the inferior face:

Фtotal = Ф100m + Фground

Where Ф = E*A*cos(α). α is the angle between the area vector and the field (180° at the topo and 0° at the bottom):

Фtotal = E100*A*cos(180°) + Eground*A*cos(0°)

Фtotal = 70A*(-1) + 130*A*1

Фtotal = 60A

By Gauss' Law, the flux is:

Фtotal = q/ε, where q is the charge, and ε is the permittivity constant in vacuum = 8.854x10⁻¹² C²/N.m²

A = 100mx100m = 10000 m²

q = 60*10000*8.854x10⁻¹²

q = 5.31x10⁻⁶ C

8 0
3 years ago
If a gas is initially at a pressure of 9 atm, a volume of 21 liters, and a temperature of 253 K, and then the pressure is raised
alex41 [277]

Answer:

15.04 mL

Explanation:

Using Ideal gas equation for same mole of gas as

\frac {{P_1}\times {V_1}}{T_1}=\frac {{P_2}\times {V_2}}{T_2}

Given ,  

V₁ = 21 L

V₂ = ?

P₁ = 9 atm

P₂ = 15 atm

T₁ = 253 K

T₂ = 302 K

Using above equation as:

\frac {{P_1}\times {V_1}}{T_1}=\frac {{P_2}\times {V_2}}{T_2}

\frac {{9}\times {21}}{253}=\frac {{15}\times {V_2}}{302}

Solving for V₂ , we get:

<u>V₂ = 15.04 mL</u>

3 0
3 years ago
A sealed piston contains 400 mL of air at standard ambient pressure. The piston is
nydimaria [60]

Answer:

324.24 kPa

Explanation:

Given that;

Initial pressure P1 = 101325 Pa

V1= 400 ml

P2 = ?

V2= 125mL

From Boyle's law;

P1V1 = P2V2

P2 = P1V1/V2

P2= 101325 × 400/125

P2= 324.24 kPa

5 0
3 years ago
what is the theoretical yield (in mols) of magnesium when 1.1 x 102 mols of lithium reacts with excess magnesium chloride.
Bezzdna [24]

Explanation:

Use the molecular formula to find the molar mass; to obtain the number of moles, divide the mass of compound by the molar mass of the compound expressed in grams.

6 0
3 years ago
Sirius, the brightest star, is 8.8 light-years from Earth. That means
Luda [366]
C) we can see Sirius as it looked 8.8 light years ago.
6 0
4 years ago
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