Answer:
C. Scientists accepted the model at first but later rejected it.
Explanation:
Scientists accepted the model at first because it explained the hydrogen emission spectrum.
However, with the development of quantum mechanics, scientists had to modify the model (not reject it).
Electrons still had specific energies, but they no longer travelled in fixed orbits.
Instead, electrons had a probability of being found in a given region of space.
Evolved. the reason why is because mabye they got trapped or something in san francisco, and since they couldnt go back to japan, they had to evolve into san francisco in order to stay alive
Answer: B. High precision
Explanation:
C. The formation of precipatation
<h3>
Answer</h3>
HF
<h3>Explanation</h3>
A buffer solution contains <em>a weak acid</em> and<em> its conjugate base</em>. The two species shall have a similar concentration in the solution. It's also possible for <em>a weak base</em> and <em>its conjugate acid</em> to form a buffer solution.
The KF solution already contains large number of
ions. The objective is to thus find its conjugate acid or base.
contains no proton
and is unlikely to be a conjugate acid. Assuming that
is a conjugate base. Adding one proton to
would produce its conjugate acid.

Therefore
is the conjugate acid of
.
happens to be a weak acid. As a result, combining
with
would produce a solution with large number of both the weak acid and its conjugate base, which is a buffer solution by definition.