Which statement is true about drying after carbonate addition?

• A. Immediately dry in an oven maintained at 110 ± 5 °C.
• B. Dry the sample at 25 °C in air.
• C. Dry at 200 °C for 30 minutes.
• D. Drying is not required after carbonate addition.

Answer: (A)

When a sample has carbonate added, you must remove moisture so you’re weighing a stable, dry mass for accurate results. Drying at 110 ± 5 °C provides a safe, reliable temperature that drives off free water quickly without affecting the sample's chemistry or causing loss of volatile components. Drying at 25 °C would be too slow and may leave moisture behind, skewing measurements. Drying at 200 °C could cause loss or alteration of components in the sample, leading to incorrect results. And skipping drying altogether would leave moisture that can interfere with subsequent steps. So drying immediately in an oven set around 110 °C is the correct practice.