Which equation shows a physical change? A. Pb(NO3)2 (aq) + 2KI(aq) → 2KNO3(aq) + PbI2(s)
B. HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)
C.2H2O(l) → 2H2(g) + O2(g)
D. H2O(g) → H2O(s)

The correct option is D

Explanation:

A physical change is a change in which no new substance is formed and can be easily reversible.

Of the options provided, option D is correct because gaseous water (steam) can be converted to solid water (ice) through freezing and can be reversed by heating up the solid water. Thus, this process does not involve the formation of any new substance.

Note that the processes of freezing and heating described must pass through the liquid phase.

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.

answer is: naturally occurring solid, inorganic compound or element is mineral.

minerals usually have crystalline form, that means than crystal constituents (atoms, molecules or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions.

for example magnetite is a mineral of iron oxide (fe₂o₃).

calcite is a carbonate mineral and the most stable polymorph of calcium carbonate (caco₃).

dolomite is an   carbonate mineral composed of calcium magnesium carbonate (camg(co₃)₂).