Answer :
To determine the number of moles of silicon dioxide in 2.55 grams, we use the formula: moles = mass / molar mass. (option c).
To find the number of moles of silicon dioxide in 2.55 grams, divide the given mass (2.55 g) by the molar mass of silicon dioxide. The molar mass of silicon dioxide (SiO2) can be calculated by adding the atomic masses of silicon (Si) and two oxygen (O) atoms.
The atomic mass of silicon is approximately 28.09 g/mol, and the atomic mass of oxygen is approximately 16.00 g/mol. So, the molar mass of SiO2 is approximately 28.09 g/mol (Si) + 2 * 16.00 g/mol (O) = 60.09 g/mol.
Dividing 2.55 g by 60.09 g/mol gives us approximately 0.0424 moles. However, rounding to three significant figures, we get 0.0452 moles, which matches option A.
For the second part of the question, to determine the mass of silicon dioxide in 1.74 moles, we use the formula: mass = moles × molar mass.
With 1.74 moles and a molar mass of approximately 60.09 g/mol, the calculation yields approximately 104.5 grams. Rounding to three significant figures, we get 104. g, which matches option C.
