Brainliestttme : )

a student wrote a chemical equation as shown.

2h2s + 3o2 → h2o + so2

what should the student do to balance the equation?

add a coefficient 4 before h2o and a 2 before so2.
add a coefficient 2 before h2o and a 4 before so2.
add a coefficient 5 before h2o and a 4 before so2.
add a coefficient 2 before h2o and a 2 before so2.

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.

It would be c. risk.