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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A scientist fills a large, tightly sealed balloon with 75,000 mL of helium at STP.

pav-90 [236]

Considering the definition of STP conditions, 3.35 moles of helium are contained within the balloon.

<h3>Definition of STP condition</h3>

The STP conditions refer to the standard temperature and pressure. Pressure values at 1 atmosphere and temperature at 0 ° C are used and are reference values for gases. And in these conditions 1 mole of any gas occupies an approximate volume of 22.4 liters.

<h3>Amount of moles of helium within the balloon</h3>

In this case, you know that scientist fills a large, tightly sealed balloon with 75,000 mL of helium at STP.

So, you can apply the following rule of three: if by definition of STP conditions 22.4 liters are occupied by 1 mole of helium, 75 L (75 L= 75000 mL, being 1 L= 1000 L) are occupied by how many moles of helium?

$amount of moles of helium=\frac{75 Lx1 mole}{22.4 L}$