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?
Responses-
a- 1.251×10^23
b- 2.049×10^23
c- 1.503×10^23
d- 6.022×10^23
To solve this problem, we first need to calculate the number of moles of silicon dioxide in the sample:
15 g SiO2 x 1 mol SiO2/60.08 g = 0.249 mol SiO2
Then, we can use Avogadro's number (6.022 x 10^23) to convert from moles to molecules:
0.249 mol SiO2 x 6.022×10^23 molecules/mol = 1.503×10^23 molecules SiO2
Therefore, the answer is (c) 1.503×10^23.
To determine the number of molecules of silicon dioxide (SiO2) in a 15-gram sample, we need to use the molar masses of silicon and oxygen.
The molar mass of SiO2 can be calculated by adding the molar masses of silicon and oxygen:
Molar Mass of SiO2 = (Molar Mass of silicon) + 2 * (Molar Mass of oxygen)
= 28.09 + 2 * 16.00
= 60.09 g/mol
To find the number of molecules in the 15-gram sample, we can use the relationship:
Number of Molecules = (Mass of the sample) / (Molar Mass of the compound) * Avogadro's Number
Number of Molecules = (15 g) / (60.09 g/mol) * (6.022 × 10^23 molecules/mol)
Calculating the result:
Number of Molecules = 0.2497 * (6.022 × 10^23 molecules)
≈ 1.503 × 10^23 molecules
Therefore, the answer is c- 1.503 × 10^23.
To determine the number of molecules of silicon dioxide (SiO2) in a 15-gram sample, you need to use the molar masses of silicon (Si) and oxygen (O) to calculate the molar mass of SiO2.
Given molar masses:
- Silicon (Si): 28.09 g/mol
- Oxygen (O): 16.00 g/mol
The molar mass of SiO2 can be calculated by adding the molar masses of Si and two O atoms:
Molar mass of SiO2 = (1 × molar mass of Si) + (2 × molar mass of O)
Molar mass of SiO2 = (1 × 28.09 g/mol) + (2 × 16.00 g/mol)
Molar mass of SiO2 = 28.09 g/mol + 32.00 g/mol
Molar mass of SiO2 = 60.09 g/mol
Now, let's use the molar mass of SiO2 to calculate the number of molecules in the 15-gram sample.
Number of moles = mass / molar mass
Number of moles of SiO2 = 15 g / 60.09 g/mol
Number of molecules = number of moles × Avogadro's number
Number of molecules of SiO2 = (15 g / 60.09 g/mol) * 6.022 × 10^23 molecules/mol
Calculating the result:
Number of molecules of SiO2 = 1.503 × 10^23 molecules
Therefore, the correct answer is option c: 1.503 × 10^23.