The reaction system represented below is at equilibrium. which of the following will decrease the amount cao(s) in the system?

caco3(s) > cao(s) + co2(g)

δhº = 178 kj/molrxn

removing some co2(g) at constant temperature
increasing the volume of the reaction vessel at constant temperature
lowering the temperature of the system
removing some caco3(s) at constant temperature

Answer; carbon monoxide (co);

Radon-222 or rn-222 has a half-life of 3.82 days. to determine the fraction of an original sample of rn-222 that remains unchanged after 7.646 days, we calculate the amount of rn-222 remaining after 7.646 days and divide it with the original amount. using 1 gram as a basis and using half-life calculation methods, we can determine that  0.249 or 0.25  grams of rn-222 will remain, and thus the fraction remaining is 0.25 or 1/4.

Is there a c and d?