There are three significant figures, this is because the zero before the decimal does not count
Answer:
Neutral substance is the one that neither exhibits acidic properties nor basic. Such a type of substance has equal no. of hydrogen and hydroxyl ions. Due to the neutrality state these substances do not show changes in the indicators.
Hydroxide ion is a strong and would react with H+ to form water
OH-+H+---->H2O
Answer:
The answer is

Explanation:
The energy of a quantum of light can be found by using the formula
<h3>E = hf</h3>
where
E is the energy
f is the frequency
h is the Planck's constant which is
6.626 × 10-³⁴ Js
From the question
f = 4.31 × 10¹⁴ Hz
We have
E = 4.31 × 10¹⁴ × 6.626 × 10-³⁴
We have the final answer as

Hope this helps you