Answer:
= 7.66 x 10²¹ oxygen atoms in 0.364 grams of CaSO₄·2H₂O
Step-by-step explanation:
For problems like this posting, one needs an understanding of the following topics:
The definition of the mole
1 mole of substance = mass in grams of substance containing 1 Avogadro's Number ( = 6.023 x 10²³ ) of particles of the specified substance. This is generally one formula weight of the substance of interest. From this, the following equivalent relationships should be memorized:
1 mole = 1 formula weight = 1 mole weight (g)= 6.023 x 10²³ particles
Converting grams to moles:
Given grams => moles = grams/gram formula wt
Converting moles to grams:
Given moles => grams = moles x gram formula wt
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Calculate the number of O atoms in 0.364 g of CaSO₄ · 2H₂O.
Given mass CaSO₄ · 2H₂O = 0.364 grams
Formula Wt CaSO₄ · 2H₂O = 172 g/mole
moles CaSO₄ · 2H₂O = mass CaSO4 · 2H2O / formula Wt. CaSO₄ · 2H₂O
= 0.364 g CaSO₄·2H₂O / 172 g CaSO4·2H2O
= (0.364/172) mole CaSO₄·2H₂O
= 2.12 x 10⁻³ mole CaSO₄·2H₂O
∴ number of Oxy (O) atoms in 0.364 grams CaSO₄·2H₂O
= (2.12 x 10⁻³ mole CaSO₄ · 2H₂O)(6.023 x 10²³ molecules CaSO₄· 2H₂O/ mole)
= 1.276876 x 10²¹molecules CaSO₄· 2H₂O CaSO₄2H₂O
= 1.276876 x 10²¹ molecules CaSO₄· 2H₂O x 6 oxygen atoms / molecule
= 7.661256 x 10²¹ oxygen atoms in 0.364 grams of CaSO₄·2H₂O
= 7.66 x 10²¹ oxygen atoms in 0.364 grams of CaSO₄·2H₂O