Question

Using the sample in question 3, how many counts per second would be observed when the detector is 10 meters away from the sample? 5. If a 10 gram sample of a radioactive substance has a half-life of 6000 years, how much would be present after 8000 years? 6. If Nitrogen-14 absorbs an alpha particle and then emits a Hydrogen-1, what is the resulting nucleus? 7. If Au-185 emits an alpha particle, what is the nucleus formed? 8. What nucleus emits an alpha particle and forms Th-234? 9. If Th-234 emits a beta particle, what nucleus is formed? 10. If Nitrogen-14 absorbs a neutron and then emits a Hydrogen-1, what nucleus is formed

Answer 1

3.Using the sample in question 3, how many counts per second would be observed when the detector is 10 meters away from the sample?

3. If a sample emits 1,000 counts per second when the detector is 1 meter from the sample, how many counts per second would be observed when the detector is 2 meters from the sample?

Doubling the distance will result in a count of (1/2)^2= 1/4 the original
count. 1/4 of 1000 = 250 counts per minute.

5.If a 10 gram sample of a radioactive substance has a half-life of 6000 years, how much would be present after 18000 years?

Answer.

18,000 ÷ 6000 = 3 half-lifes
Each half-life, one half of the radioactive substance decays.

20 – 10 = 10
10 – 5 = 5
5 – 2.5 = 2.5 grams

OR
N = No * ½ ^n
n = 3
½ ^3 = 1/8
N = 20 * ½ ^3 = 2.5 grams

6.If Nitrogen-14 absorbs an alpha particle and then emits a Hydrogen-1, what is the resulting nucleus?

Answer.  

Sounds like Carbon 14 to me. Nitrogen is atomic number 7. If it is nitrogen 14, then it also has seven neutrons. Add a neutron - Nitrogen 15. Spit out a proton, you have Carbon 14 - the stuff used to date old dead organic stuff.

7.If Au-185 emits an alpha particle, what is the nucleus formed?

(185 Au 79)gold - (4 α 2) = (181 X 77) .. .. ►(181 Ir 77) .. Iridium isotope

8.What nucleus emits an alpha particle and forms Th-234?

In beta decay, a neutron is converted to a proton and a W- boson is emitted, which decays into an electron and electron antineutrino. Because the neutron is converted to a proton, the atomic number goes up by one, but because it is converted to a neutron, the atomic mass does not change.

238-U decays via alpha decay to form 234-Th. 234-Th decays via emission of a beta- particle to form 234-Pa.

9.If Th-234 emits a beta particle, what nucleus is formed?

The proton stays in the nucleus, increasing the atomic number of the atom by one. The electron is ejected from the nucleus and is the particle of radiation called beta. Thorium-234 is a nucleus that undergoes beta decay. Here is the nuclear equation for this beta ^decay.

^{10.  If Nitrogen-14 absorbs a neutron and then emits a Hydrogen-1, what nucleus is formed?}

^Answer.

^{N14 + 1n = N15
N15 - H1 = C14}

^(or)

The reaction:

¹⁴₇ N +¹₀ n ¹₁ H + ^A_Z X

<sup>The sum of the mass numbers and the sum of the atomic numbers must be the same on both sides of the reaction.

The mass numbers:</sup>

^{14+1 = A+1}

^{14+1-1 =A}

^14=A

The atomic numbers:

7+0 =1+Z

7-1 =Z

Z=6.

The formed nucleus has the atomic number 6, so it's a nucleus of carbon.

¹⁴₇ N +¹₀ n ¹₁ H + ¹⁴₆ C

A nucleus of carbon-14 is formed.