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Serotonin (C10H12N2O)₄; molar mass = 176 g mol⁻¹) is a compound that conducts nerve impulses in the brain and muscles - VCE - SSCE Chemistry - Question 2 - 2008 - Paper 1
Question 2
Serotonin (C10H12N2O)₄; molar mass = 176 g mol⁻¹) is a compound that conducts nerve impulses in the brain and muscles. A sample of spinal fluid from a volunteer in a... show full transcript
Worked Solution & Example Answer:Serotonin (C10H12N2O)₄; molar mass = 176 g mol⁻¹) is a compound that conducts nerve impulses in the brain and muscles - VCE - SSCE Chemistry - Question 2 - 2008 - Paper 1
Step 1
Calculate the number of moles of serotonin in one millilitre
Answer
The concentration of serotonin is given as 1.5 ng/L. To find the amount in millilitres, we first convert ng to g:
1.5 ng = 1.5 x 10⁻⁹ g.
Since there are 1000 mL in 1 L:
Amount in 1 mL = (1.5 x 10⁻⁹ g/L) × (1 L / 1000 mL) = 1.5 x 10⁻¹² g/mL.
Next, we calculate the number of moles using the molar mass (176 g/mol):
Number of moles = mass (g) / molar mass (g/mol) = (1.5 x 10⁻¹² g) / (176 g/mol) = 8.52 x 10⁻¹⁴ mol.
Step 2
Calculate the number of molecules of serotonin
Answer
Using Avogadro's number (approximately 6.022 x 10²³ molecules/mol):
Number of molecules = number of moles × Avogadro's number = (8.52 x 10⁻¹⁴ mol) × (6.022 x 10²³ molecules/mol) = 5.13 x 10⁹ molecules.
Thus, the final answer is A. 5.13 x 10⁹.