Radiocarbon Dating

Q. Which of the following isotopes is used in radiocarbon dating?

1. Carbon-8
2. Carbon-11
3. Carbon-14
4. Carbon-9

Q.

How do we know the age of the fossils?

Q. A sample of ${}_{53}^{131}I$, as iodide ion, was administered to a patient in a carrier consisting of $10\sqrt{2}mg$ of iodide ion. After $4.0$ days $10\%$ of the initial radioactivity was detected in the thyroid gland of the patient. What mass (in mg) of the iodide ion had migrated to the thyroid gland? Half-life ${}_{53}^{131}I$ is $8.0$ days.

Q. A sample of $U^{238}(t_{1/2}=4.5\times {10}^{9}years)$ ore is found to contain 23.8 g of $U^{238}$ and 20.6 g of $P{b}^{206}$. Calculate rate constant of the rock.

Q. A wooden piece is $11520$ yrs old. What is the fraction of ${}^{14}C$ activity left in the piece?

1. $0.12$
2. $0.25$
3. $0.50$
4. $0.75$

Q. The half life of a radioactive element is $10$ hrs. How much be left after $4$ hrs in $1$ gm atom sample?

Q. Wooden article and freshly cut tree show activity of 7.6 and 15.2 min${}^{-1}$g${}^{-1}$ of carbon $(t_{1/2}=5760year)$ respectively. The age of the article is:

1. $5760\times (15.2-7.6)year$
2. $5760year$
3. $5760\times \frac{15.2}{7.6}year$
4. $5760\times \frac{7.6}{15.2}year$

Q. Living things contain carbon in two forms, $carbon-12$ which is stable and $carbon-13$ that decays and declines in proportionate quantity. The technique that uses this principle for determining the age of fossils, skeletons, old trees and dinosaurs is known as:

1. Fossil carbon
2. Radio-carbon dating
3. $Carbon-12$ dating
4. The Carbon Age

Q. A piece of wood from an archaeological source shows a ${}^{14}C$ activity which is $60$% of the activity found in fresh wood today. The age of archaeological sample will be:

1. $4246$ yrs
2. $4628$ yrs
3. $4624$ yrs
4. $6248$ yrs

Q. An analysis of the rock shows that the relative number of $S{r}^{87}$ and $R{b}^{87}(t_{1/2}=4.7\times {10}^{10}year)$ atoms is $\mathrm{0.05.}$ What is the age of the rock ? Assume all $S{r}^{87}$ to be formed from $R{b}^{87}$ only.

1. $7.62\times {10}^9$ year
2. $1.43\times {10}^9$ year
3. $4.32\times {10}^8$ year
4. $3.28\times {10}^9$ year

Q. In the process of photosynthesis, $O_2$ gas is released from:

1. $C{O}_2$
2. $H_{2}O$
3. both $H_{2}O$ and $C{O}_2$
4. mechanism is not confirmed

Q. A piece of wood from an archeological source shows a ${}^{14}C$ activity which is $60\%$ of the activity found in fresh wood today. Calculate the age of the archeological sample. $(t_{1/2}\text{of}{}^{14}C=5770year)$.

Q. Half-life for radioactive ${}^{14}C$is 5760 years. in how many years 200 mg of ${}^{14}C$ will be reduced to 25 mg?

1. 17280 years
2. 23040 years
3. 5760 years
4. 11520 years

Q. The isotope of uranium used as a fuel in nuclear reactors and carbon used in radiocarbon dating are:

1. $U-233$ and $C-13$
2. $U-235$ and $C-14$
3. $U-233$ and $C-14$
4. $U-235$ and $C-13$

Q. The amount of ${}_6{C}^{14}$ isotope in a piece of wood is found to one fourth $\left(1/4\right)$ of that present in afresh piece of wood. Calculate the age of the piece of wood $(t_{1/2}of{}_6{C}^{14}=5770years)$

1. $7999$ year
2. $11540$ year
3. $16320$ year
4. $23080$ year

Q. Assertion :The archaeological studies are based on the radioactive decay of carbon-$14$ isotope. Reason: The ratio of $C-14$ to $C-12$ in the animals or plants is the same as that in the atmosphere.

1. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
2. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
3. Assertion is correct but Reason is incorrect
4. Both Assertion and Reason are incorrect

Q. Explain radiocarbon dating.

Q. The ${\beta }^{-}-activity$ of a sample of $C{O}_2$ prepared from a contemporary wood gave a count rate of $25.5$ counts per minute (c.p.m.). The same mass of $C{O}_2$ from an ancient wooden statue gave a count rate of $20.5$ cpm, in the same counter condition. Calculate its age to the nearest $50year$ taking $t_{1/2}$ for ${}^{14}C$ as $5770$ year. What would be the expected count rate of an identical mass of $C{O}_2$ from a sample which is $4000$ year old?

Q. A sample of ${}^{238}U$(half-life$=4.5\times {10}^9$ yr) ore is found to contain $23.8$g of ${}^{238}U$ and $20.6$g of ${}^{206}Pb$. Calculate the age of the ore.

Q. A sample of rock from moon contains equal number of atoms of uranium and lead $(t_{1/2}forU=4.5\times {10}^{9}years)$. The age of the rock would be:

1. $4.5\times {10}^9$ years
2. $9\times {10}^9$ years
3. $13.5\times {10}^9$ years
4. $2.25\times {10}^9$ years