Answer:
<em>= 7.66 x 10²¹ oxygen atoms in 0.364 grams of CaSO₄·2H₂O</em>
Explanation:
For problems like this posting, one needs an understanding of the following topics:
The definition of the mole
<u>1 mole of substance</u> = 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:
<em> 1 mole = 1 formula weight = 1 mole weight (g)= 6.023 x 10²³ particles</em>
Converting grams to moles:
<em>Given grams => moles = grams/gram formula wt </em>
Converting moles to grams:
<em>Given moles => grams = moles x gram formula wt</em>
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<em>Calculate the number of O atoms in 0.364 g of CaSO₄ · 2H₂O.</em>
Given mass CaSO₄ · 2H₂O = 0.364 grams
Formula Wt CaSO₄ · 2H₂O = 172 g/mole
moles CaSO₄ · 2H₂O = mass <em>CaSO4 · 2H2O / formula Wt. CaSO₄ · 2H₂O</em>
<em>= 0.364 g CaSO₄·2H₂O </em><em>/ </em><em>172 g CaSO4·2H2O </em>
<em>= (0.364/172) mole CaSO₄·2H₂O </em>
<em>= 2.12 x 10⁻³ mole CaSO₄·2H₂O </em>
<em>∴ number of Oxy (O) atoms in 0.364 grams CaSO₄·2H₂O </em>
<em>= (2.12 x 10⁻³ mole CaSO₄ · 2H₂O)(6.023 x 10²³ molecules CaSO₄· 2H₂O/ mole)</em>
<em>= 1.276876 x 10²¹molecules CaSO₄· 2H₂O CaSO₄2H₂O </em>
<em>= 1.276876 x 10²¹ molecules CaSO₄· 2H₂O x 6 oxygen atoms / molecule</em>
<em>= 7.661256 x 10²¹ oxygen atoms in 0.364 grams of CaSO₄·2H₂O</em>
<em>= 7.66 x 10²¹ oxygen atoms in 0.364 grams of CaSO₄·2H₂O</em>
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