Observe the statements. I. Phenolphthalein is a colourless solution II. Phenolphthalein turns pink in basic solution III. Phenolphthalein turns red in acidic solution IV. Phenolphthalein remains colourless in acidic solution Choose the correct option a. I &II are correct b. I & III are correct c. I ,II & IV are correct d. All the statements are correct

c.I ,II & IV are correct

Explanation:

Phenolphthalein is an indicator. An indicator is an organic dye whose solution changes colour as the concentration of hydrogen ions in solution changes.

Hence a typical indicator exhibits different colours at different pH ranges. The colour of an indicator in an acid, a base and at end point always differs.

Phenolphthalein  is a colourless solution which has a pink colour in an alkaline medium and colourless in an acidic medium.

- lead + phosphoric acid = hydrogen + lead(ii) phosphate

the ideal gas law equation is as follows

pv = nrt

where p - pressure

v - volume

n - number of moles

r - universal gas constant

t - temperature

so if the pressure, volume and temperature are already known

we are left with n and r

since r is the universal gas constant that has a known fixed value then r too is known

so we are left with 'n'

once we know temperature volume and pressure

we can find the number of moles of gas present using the ideal gas law equation

this is not my own answer, this is an answer for the same question by the user blahblahmali. i do not claim ownership of this account.