Radio active decay reactions follow first order rate kinetics.
a) The half life and decay constant for radio active decay reactions are related by the equation:
Where k is the decay constant
b) Finding out the decay constant for the decay of C-14 isotope:
c) Finding the age of the sample :
35 % of the radiocarbon is present currently.
The first order rate equation is,
![[A] = [A_{0}]e^{-kt}](https://tex.z-dn.net/?f=%20%5BA%5D%20%3D%20%5BA_%7B0%7D%5De%5E%7B-kt%7D%20%20%20)
![\frac{[A]}{[A_{0}]} = e^{-kt}](https://tex.z-dn.net/?f=%20%5Cfrac%7B%5BA%5D%7D%7B%5BA_%7B0%7D%5D%7D%20%3D%20e%5E%7B-kt%7D%20%20)
t = 7923 years
Therefore, age of the sample is 7923 years.
We must to know:
Cm = molarity = niu / Vs, when the niu = no. of moles and Vs = Volume of solution
the no. niu = mass / molecular mass of substance
molecular mass of C8H8 = 12x8+8x1 = 104 g/mol
=> niu = 1,5 / 104 = 0,0144 moles C8H8
=> Cm = 0,0144/0,225 = 0,06 mol/L
Cmm = molality = niu (C8H8) / mass of solvent (kg)
=> p = mass / V => mass (solvent) = p x V
=> 225 x 1,02 = 229,5 g solvent = 0,2295 kg solvent
=> Cmm = 0,0144 / 0,229,5 = 0,063
The statement that defines the specific heat capacity for a given sample is the quantity of heat that is required to raise 1 g of the sample by 1°C (Kelvin) at a constant pressure.
<h3>What is specific heat capacity?</h3>
Specific heat capacity is the of heat to increase the temperature per unit mass.
The formula to calculate the specific heat is Q = mct.
The options are attached here:
- The temperature of a given sample is 1 %.
- The temperature that a given sample can withstand.
- The quantity of heat that is required to raise the sample's temperature by 1 °C1 °C (Kelvin).
- The quantity of heat that is required to raise 1 g of the sample by 1°C (Kelvin) at a constant pressure.
Thus, the correct option is 4. The quantity of heat that is required to raise 1 g of the sample by 1°C (Kelvin) at a constant pressure.
Learn more about specific heat capacity
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Answer:
- What distinguish a solution in general from an aqueous solution is the solvent. A solution in general may contain any solvent, which may be solid, liquid or gas, while an aqueous solution is formed with water as solvent.
Explanation:
A solution in general is a homogeneous mixture in which a substance, named solute, is dissolved, in other substance, name solvent.
Solutions may be in solid, liquid or gas state. There are many kind of solvents. Usually, in a lab you work with liquid solutions. Some liquid solvents are: ethanol, glycerin, hexane, benzene, and water, among many others.
Aqueous solution is a solution where the solvent is water. Of course, the solute may be any one: NaCl, sugar, ethanol, an acid, a base, a salt.
What distinguish a solution in general and an aqueous solution is the solvent.
When highly electronegative element like oxygen is directly attached to less electronegative element like hydrogen the electrons from less electronegative elements are attracted toward the highly electronegative element, making the less electronegative element deficient in electron density (partial positive) and a partial negative charge on more electronegative element is created. In such situation the intermolecular forces formed are dipole-dipole interactions or hydrogen bond interaction like in HF.
