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3 years ago

Technetium-99m, a “metastable” nuclide of

1 answer:

4 0

In beta decay, a neutron is transformed into a proton via emission of an electron. This means that the total nucleon number remains the same; however, the proton number is increased by one (and the neutron number decreases by one). Therefore, the parent atom must also have mass number 99 but be of one less atomic number.
The atomic number of Tc is 43 and proton number 42 is Mo. Therefore, the answer is:
99Mo

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How is a radioactive element different from a stable element?

USPshnik [31]

A radioactive element has an unstable nucleus that emits particles in the form of alpha, beta, or gamma radiation. A stable element has a nucleus that does not emit such particles

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2 years ago

Find the force of gravity of 1000 kg car.

ANEK [815]

Answer:

The force of gravity acting on the car is <u>9800 N vertically downward.</u>

Explanation:

Given:

Mass of the car given is 1000 kg.

We know that the force of gravity is the force applied by the center of Earth on any body. The force of gravity is also called the weight of the body and always act towards the center of the Earth.

From Newton's second law, we know that the force acting on a body is equal to its mass and acceleration.

Here, the acceleration acting on the car is due to gravity and thus has a constant value of 9.8 m/s² on the surface of Earth.

Therefore, the force of gravity acting on the car is given using the Newton's second law as:

Force of gravity = Mass of car $\times$ Acceleration due to gravity.

Force of gravity = (1000 kg) $\times$ (9.8 m/s²)

Force of gravity = 9800 N [1 kg.m/s² = 1 N]

Therefore, the force of gravity acting on the car is 9800 N vertically downward.

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3 years ago

Which best describe the isovolumetric contraction phase of the cardiac cycle?

cluponka [151]

The name isovolumetric indicates that there is no change in volume that takes place and this only occurs when all of the valves within the heart are shut.

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3 years ago

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Which reaction occurs spontaneously

coldgirl [10]

Answer:

Chemical Reaction

Explanation:

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3 years ago

if i add 25 ml of water to 135 ml of a 0.25 M NaOH solution what will the molarity of the diluted solution be

DENIUS [597]

Answer:

0.21 M. (2 sig. fig.)

Explanation:

The molarity of a solution is the number of moles of the solute in each liter of the solution. The unit for molarity is M. One M equals to one mole per liter.

How many moles of NaOH in the original solution?

$n = c \cdot V$ ,

where

$n$ is the number of moles of the solute in the solution.
$c$ is the concentration of the solution. $c = 0.25 \;\text{M} = 0.25\;\text{mol}\cdot\textbf{L}^{-1}$ for the initial solution.
$V$ is the volume of the solution. For the initial solution, $V = 135\;\textbf{mL} = 0.135\;\textbf{L}$ for the initial solution.

$n = c\cdot V = 0.25\;\text{mol}\cdot\textbf{L}^{-1} \times 0.135\;\textbf{L} = 0.03375\;\text{mol}$ .

What's the concentration of the diluted solution?

$\displaystyle c = \frac{n}{V}$ .

$n$ is the number of solute in the solution. Diluting the solution does not influence the value of $n$ . $n = 0.03375\;\text{mol}$ for the diluted solution.
Volume of the diluted solution: $25\;\text{mL} + 135\;\text{mL} = 160\;\textbf{mL} = 0.160\;\textbf{L}$ .

Concentration of the diluted solution:

$\displaystyle c = \frac{n}{V} = \frac{0.03375\;\text{mol}}{0.160\;\textbf{L}} = 0.021\;\text{mol}\cdot\textbf{L}^{-1} = 0.021\;\text{M}$ .

The least significant number in the question comes with 2 sig. fig. Keep more sig. fig. than that in calculations but round the final result to 2 sig. fig. Hence the result: 0.021 M.

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3 years ago

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