Use the table of molar masses to answer the question
Element: | Molar mass (g/mol):
Silicon 28.09
Oxygen 16.00
How many molecules of silicon dioxide (SiO₂) are there in a 15-gram sample?
A. 6.022 x 10^23
B. 1.503 x 10^23
C. 2.049 x 10^23
D. 1.251 x 10^23
Si O2 = 28.09 + 32 = 60.09 grams/mol
15 / 60.09 = 0.2496 mols
0.2496 mols * 6.022*10^23 molecules/mol = 1.5032 *10^23 molecules
Well, let's calculate it step by step. The molar mass of SiO₂ is the sum of the molar masses of one silicon atom and two oxygen atoms. So, it would be 28.09 grams/mol + (16.00 grams/mol * 2) = 60.09 grams/mol.
Now, to find the number of molecules in a 15-gram sample, we need to use Avogadro's number. Avocado, oops, I mean Avogadro's number is 6.022 x 10²³ molecules/mol.
So, we divide the mass of the sample (15 grams) by the molar mass (60.09 grams/mol) and then multiply it by Avogadro's number.
(15 grams / 60.09 grams/mol) * (6.022 x 10²³ molecules/mol) = 1.503 x 10²³ molecules.
So, the correct answer is B. 1.503 x 10²³. Just don't bring any clowns into the lab, they tend to make a mess! 🤡🧪
To determine the number of molecules of silicon dioxide (SiO₂) in a 15-gram sample, we need to use the molar masses to convert grams to moles, and then use Avogadro's number to convert moles to molecules.
The molar mass of SiO₂ is the sum of the molar masses of silicon (Si) and oxygen (O).
Molar mass of SiO₂ = (molar mass of Si) + 2 * (molar mass of O)
= 28.09 + 2 * 16.00
= 60.09 g/mol
Now we can calculate the number of moles in the 15-gram sample of SiO₂ using the equation:
Number of moles = mass (g) / molar mass (g/mol)
= 15 g / 60.09 g/mol
= 0.2498 mol (rounded to four decimal places)
Finally, we can use Avogadro's number, which states that there are 6.022 x 10^23 entities per mole, to convert moles to molecules:
Number of molecules = number of moles * Avogadro's number
= 0.2498 mol * 6.022 x 10^23/mol
= 1.503 x 10^23 molecules (rounded to three significant figures)
Therefore, there are approximately 1.503 x 10^23 molecules of silicon dioxide (SiO₂) in a 15-gram sample.
Hence, the correct answer is B. 1.503 x 10^23.
To answer this question, we need to know the molar mass of silicon dioxide (SiO₂) and use it to calculate the number of molecules in a 15-gram sample.
The molar mass of SiO₂ can be calculated by adding the molar masses of silicon (Si) and oxygen (O).
Molar mass of SiO₂ = (Molar mass of Si) + 2 * (Molar mass of O)
= 28.09 + 2 * 16.00
= 28.09 + 32.00
= 60.09 g/mol
Now, we can use this molar mass to calculate the number of molecules in a 15-gram sample.
Number of moles = Mass of sample / Molar mass
= 15 g / 60.09 g/mol
= 0.2497 mol
To convert the number of moles to the number of molecules, we can use Avogadro's number, which is approximately 6.022 × 10^23 molecules/mol.
Number of molecules = Number of moles * Avogadro's number
= 0.2497 mol * 6.022 × 10^23 molecules/mol
= 1.503 × 10^23 molecules
Therefore, the correct answer is B. 1.503 × 10^23 molecules.