The answer is the second choice.
Answer:
11.72 grams
Explanation:
Let the equilibrium concentration of BrCl be y
Initial concentration of Br2 = number of moles ÷ volume = (0.979×1000/160) ÷ 199 = 0.031 M
Initial concentration of Cl2 = (1.075×1000/71) ÷ 199 = 0.076 M
From the equation of reaction
1 mole of Br2 reacted with 1 mole of Cl2 to form 2 moles of BrCl
Therefore, equilibrium concentration of Br2 = (0.031 - 0.5y) M while that of Cl2 = (0.076 - 0.5y) M
Kp = [BrCl]^2/[Br2][Cl2]
1.1×10^-4 = y^2/(0.031 - 0.5y)(0.076 - 0.5y)
y^2/0.002356-0.0535y+0.25y^2 = 0.00011
y^2/0.00011 = 0.002356-0.0536y+0.25y^2
9090.9y^2-0.25y^2+0.0536y-0.002356 = 0
9090.65y^2+0.0535y-0.002356 = 0
The value of y must be positive and is obtained using the quadratic formula
y = [-0.0535 + sqrt(0.0535^2 - 4×9090.65×-0.002356)] ÷ 2(9090.65) = 9.2025/18181.3 = 0.00051 M
Mass of BrCl = concentration×volume×MW = 0.00051×199×115.5 = 11.72 grams
Carbon-14 is radioactive isotope of carbon.
Carbon is essential element of living cells. While the living cells are alive, the carbon contained in them are in equilibrium with the carbon in atmosphere. But, once the cell dies, the carbon-14 isotope undergoes radioactive decay. By measuring the carbon-14 in atmosphere to the carbon-14 in dead organism, we can calculate the time (or years) that organism have died.
However, carbon-14 dating technique is not accurate for estimating the age of materials older than 50,000 years old (above 40,000 years). This is because, 99% of carbon is carbon-12, 1% is carbon-13 and trace remaining is the carbon-14. This means, carbon-14 is found in very trace amount, in fact 1 part per trillion of carbon atoms present is carbon-14. The half of life of carbon-14 is 5,730 years. For dating the organism, we use the concept of half lives of the carbon-14 isotope in the dead organisms and calculate how many half life old the sample is. But as the years increases, the number of carbon-14 isotope becomes too low to detect and make accurate calculation.
This means, at some point the organism can simply run out of carbon-14.
Hence carbon-14 dating is not accurate for estimating age of materials older than 50,000 years old.
