1. the noble gas krypton (Kr).
Answer:
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Explanation:
The balanced chemical reaction to obtain water from SnO₂ is:
The mole ratio is:

Find the number of moles equivalent to 1.20× 10²¹ molecules of water, using Avogadro's number:

From the mole ratio, the number of moles of SnO₂ are half the number of moles of water. That is:
- 0.0019927 moles / 2 = 0.00099635 moles of SnO₂
Use the molar mass of SnO₂ to convert the number of moles to grams:
- molar mass of SnO₂ = 150.71g/mol
- mass of SnO₂ = 0.00099635mol × 150.71 g/mol = 0.150 grams.
The answer must be reported with 3 significant figures.