a...if you had the fully extended periodic table, these elements would be between La and Hf in period 6 and Ac and Rf in period 7
Carbon -14 and Carbon 12 are the two substances geologists use in radiocarbon dating.
Answer: Option B
<u>Explanation:
</u>
Radiocarbon dating denotes the determination process of the age of fossils of plants or animals based on the ratio of carbon atoms 14 to 12. Carbon naturally exists in two non-radioactive isotopes, Carbon-12 and Carbon-13 and one radioactive isotope carbon 14. The carbon 14 gets released on continuous cosmic reaction with atmospheric nitrogen.
These carbon 14 will be absorbed by the living plants and from the plants. Then, it will enter inside the animals which consume the plants. But once the plants and animals died, they ceased to intake carbon-14. In their living state, the ratios of carbon atoms 14 to 12 in them tends to similar to the ratio in atmosphere.
But after they die, the ratio of C-14 to C-12 will be varying from the ratio of C-14 to C-12 in atmosphere as the concentration of C-14 will be decreasing in the dead animals and plants. Thus using this ratio, geologists can find the fossil's age.
Answer: 12.0 milliliters of 6.50 M HCl ( aq ) are required to react with 2.55 g Zn.
Explanation:
moles =
moles of zinc =
The balanced chemical equation is :
According to stoichiometry:
1 mole of zinc reacts with = 2 moles of HCl
Thus 0.0390 moles of zinc reacts with = 
moles of HCl
To calculate the volume for given molarity, we use the equation:
.....(1)
Molarity of 
solution = 6.50 M
Volume of solution = ?
Putting values in equation 1, we get:
Thus 12.0 ml of 6.50 M HCl ( aq ) are required to react with 2.55 g Zn
PV = nRT
R = 0.0821 L * atm / mol * K
(ideal gas constant)
First, convert 735 torr to atm. Divide by 760.
(1 atm = 760 torr)
735 torr * 1 atm / 760 torr = 0.967 atm
Then, convert 37 C to Kelvin. Just add 273.
37 C = 310K
n = PV / RT
= (0.967)(2.07) / (0.0821)(310)
= 0.0786 mol
<span>0.0786 mol * 6.02 * 10^23 molecules / 1 mol = 4.73 * 10^22 molecules </span>
Answer: 600 kJ
-
Explanation:
C₃H₈ (g) + 5 O₂ (g) =============== 3 CO₂ (g) + 4 H₂O (l)
Δ⁰Hf kJ/mol -104 0 -393.5 -285.8
Δ⁰Hcomb C₃H₈ = 3(-393.5) + 4 (-285.80) - (-104) kJ/mol
Δ⁰Hcomb = 2219.70 kJ/mol
n= m /MW MW c₃H₈ = 44.1 g/mol
n= 12 g/44.1 g/mol = 0.27 mol
then for 12 g the heat released will be
0.27 mol x 2219.70 kJ/mol = 600 KJ
