The reaction between excess calcium carbonate powder and 25 cm of 1.0 mol dm nitric acid shown in the following chemical equation
CaCO, (s) + 2HNO, (aq) → Ca(NO3)2 (aq) + CO: (g) + H2O (l)
(a) Calculate the mass of calcium nitrate salts formed in the solution. [RAM] : C = 12,0 = 16. Ca = 401​

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.

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