(2) U-238 is the radioisotope used in dating geological formations. Uranium-238 has a half-life of 4.46 billion years, which makes it suitable to date such old formations.
The other options do not have such long durabilities and half-lives.
Answer:
147 g
Explanation:
<em>The number of moles of a substance is the ratio of the mass of the substance and the molar mass of that substance.</em> Mathematically,
mole = mass of substance/molar mass
In this case, Nick needs 3.5 moles of NaF, the molar mass of NaF is calculated as:
23 + 19 = 42 g/mol (Note: Na = 23, F = 19)
Hence,
mass of 3.5 mole NaF = mole x molar mass
= 3.5 x 42 = 147 g.
<em>Hence, Nick would need to measure out </em><em>147 g</em><em> NaF using a suitable weighing balance.</em>
Answer: The pH 0f 0.10 solution of HCl is 1.00
Explanation:
pH or pOH is the measure of acidity or alkalinity of a solution.
pH is calculated by taking negative logarithm of hydrogen ion concentration.
![pH=-\log [H^+]](https://tex.z-dn.net/?f=pH%3D-%5Clog%20%5BH%5E%2B%5D)
According to stoichiometry,
1 mole of 
gives 1 mole of 
Thus 
moles of gives =
moles of
Putting in the values:
![pH=-\log[0.10]](https://tex.z-dn.net/?f=pH%3D-%5Clog%5B0.10%5D)
Thus pH 0f 0.10 solution of HCl is 1.00
A solution (in this experiment solution of NaNO₃) freezes at a lower temperature than does the pure solvent (deionized water). The higher the
solute concentration (sodium nitrate), freezing point depression of the solution will be greater.
Equation describing the change in freezing point:
ΔT = Kf · b · i.
ΔT - temperature change from pure solvent to solution.
Kf - the molal freezing point depression constant.
b - molality (moles of solute per kilogram of solvent).
i - Van’t Hoff Factor.
First measure freezing point of pure solvent (deionized water). Than make solutions of NaNO₃ with different molality and measure separately their freezing points. Use equation to calculate Kf.
