Answer:
pH =3.8
Explanation:
Lets call the monoprotic weak acid HA, the dissociation equilibria in water will be:
HA + H₂O ⇄ H₃O⁺ + A⁻ with Ka = [ H₃O⁺] x [A⁻]/ [HA]
The pH is the negative log of the H₃O⁺ concentration, we know the equilibrium constant, Ka and the original acid concentration. So we will need to find the [H₃O⁺] to solve this question.
In order to do that lets set up the ICE table helper which accounts for the species at equilibrium:
HA H₃O⁺ A⁻
Initial, M 0.40 0 0
Change , M -x +x +x
Equilibrium, M 0.40 - x x x
Lets express these concentrations in terms of the equilibrium constant:
Ka = x² / (0.40 - x )
Now the equilibrium constant is so small ( very little dissociation of HA ) that is safe to approximate 0.40 - x to 0.40,
7.3 x 10⁻⁶ = x² / 0.40 ⇒ x = √( 7.3 x 10⁻⁶ x 0.40 ) = 1.71 x 10⁻³
[H₃O⁺] = 1.71 x 10⁻³
Indeed 1.71 x 10⁻³ is small compared to 0.40 (0.4 %). To be a good approximation our value should be less or equal to 5 %.
pH = - log ( 1.71 x 10⁻³ ) = 3.8
Note: when the aprroximation is greater than 5 % we will need to solve the resulting quadratic equation.
Answer:
A) 4.3 × 10²⁴ atoms
Explanation:
Step 1: Given data
Moles of neon: 7.2 moles
Step 2: Calculate the number of atoms present in 7.2 moles of neon
In order to convert moles to toms, we need a conversion factor. In this case, we will use Avogadro's number: there are 6.02 × 10²³ neon atoms in 1 mole of neon atoms.
7.2 mol × 6.02 × 10²³ atoms/mol = 4.3 × 10²⁴ atoms
Answer:
Controlling the environment is the most key procedures for getting good results.
Explanation:
The control environment for an experiment is the essential part for getting good results. In control environment, there is no or less chances of disruption
from the external environment which can cause the results of the data more acceptable. So the scientists prefers laboratory for performing experiment as compared to outer environment. So in my opinion for getting better results, the control environment is the most necessary experimental procedure.
