1.
How many grams are there in 1.3846 x 10^{24} atom of Silicon?
Correct Answer
A. 64.607 g
Explanation
To change from atoms to grams requires TWO steps:
1st: Change to moles: Take your atoms and DIVIDE by Avogadro’s number:
1.3846 x 10^24 divided by 6.02 x 10^23 = 2.3 moles
2nd: Change to grams: Take your moles and MULTIPLY by molar mass:
2.3 moles x 28.09 g/mol = 64.607 g
2.
How many grams are there in 2.0468 x 10^{25} atoms of NaCl? (The molar mass of NaCl is 58.44g)
Correct Answer
C. 1988.59 g
3.
How many grams are in 2.2274 x 10^{25} atoms of CO_{2}?
Correct Answer
A. 1,629 g
Explanation
Firstly, we recognize that CO2 consists of one carbon (C) atom and two oxygen (O) atoms. Carbon has a molar mass of around 12.01 grams per mole, and oxygen has a molar mass of about 16.00 grams per mole.
To find the total molar mass of CO2, we add the molar masses of carbon and two oxygen atoms together. This gives us approximately 44.01 grams per mole.
Next, we convert the number of atoms given to moles. This conversion utilizes Avogadro's number, which is about 6.022 x 10^23 atoms per mole. By dividing the given number of atoms by Avogadro's number, we find the number of moles, approximately 37 moles.
Finally, to find the mass in grams, we multiply the number of moles by the molar mass. This yields a result of approximately 1.63 x 10^3 grams which is approximately 1629 g.
4.
How many grams are in 3.3712 x 10^{25} atoms of CCl_{4}? (Molar mass of CCl_{4} is 153.81 g)
Correct Answer
B. 861.53 g
5.
How many grams are in 2.1672 x 10^{25} atoms of Glucose C_{6}H_{12}O_{6}?
(The molar mass of glucose is: 180 g/mol)
Correct Answer
D. 6498 g
6.
How many atoms are there in 118.082 g of Potassium?
Correct Answer
C. 1.818 x 10^24 atoms
Explanation
To change from grams to atoms requires TWO steps:
1st: change to moles: Take your grams and divide by molar mass.
118.082 g divided by 39.1 g = 3.02 moles
2nd: Change to atoms: Take your moles and multiply by Avogadro’s number:
3.02 x 6.02 x 10^23 = 1.818 x 10^24
7.
How many atoms are there in 70.554 g of Sulfur?
Correct Answer
D. 1.32 x 10^24 atoms
Explanation
To change from grams to atoms requires TWO steps:
1st: change to moles: Take your grams and divide by molar mass.
70.554 g divided by 32.07 g = 2.2 moles
2nd: Change to atoms: Take your moles and multiply by Avogadro’s number:
2.2 x 6.02 x 10^23 = 1.32 x 10^24
8.
How many atoms are there in 80.223 g of Magnesium?
Correct Answer
A. 1.99 x 10^24 atoms
Explanation
To change from grams to atoms requires TWO steps: 1st: change to moles: Take your grams and divide by molar mass. 80.223 g divided by 24.31 g = 3.3 moles 2nd: Change to atoms: Take your moles and multiply by Avogadro’s number: 3.3 x 6.02 x 10^23 = 1.99 x 10^24 atoms
9.
How many atoms are there in 18.02 g of H_{2}O? (Hint: How many atoms are the in each molecule of H_{2}O?)
Correct Answer
C. 1.8 x 10^24 atoms
10.
How many atoms are there in 148.375 g of LiCl? (Hint: How many atoms are found in each LiCl?)
(Use molar mass for LiCl = 42.394)
Correct Answer
D. 4.26 x 10^24 atoms
11.
What is the mass in grams of 3.01 x 10^24 atoms of carbon (C)? (Molar mass of carbon is 12.01 g/mol)
Correct Answer
C. 5.02 x 10^-22 grams
Explanation
To determine the mass in grams of 3.01 x 10^24 atoms of carbon, we first utilize the concept of molar mass, representing the mass of one mole of a substance. Carbon's molar mass is 12.01 g/mol. We then employ Avogadro's number, which states that one mole of any substance contains 6.022 x 10^23 atoms. Using the formula Mass (g) = Number of atoms × (Molar mass (g/mol) ÷ Avogadro's number), we substitute the given values to calculate the mass. Consequently, the result is 5.02 x 10^-22 grams, corresponding to option c) 5.02 x 10^-22 grams.
12.
How many atoms are there in 25.0 g of magnesium (Mg)? (Molar mass of magnesium is 24.31 g/mol)
Correct Answer
A. 6.02 x 10^23 atoms
Explanation
The process begins by determining the number of atoms present in 25.0 g of magnesium. We employ the molar mass of magnesium, which is 24.31 g/mol. Utilizing Avogadro's number, we ascertain that one mole of magnesium contains 6.022 x 10^23 atoms. Employing the formula Number of atoms = (Mass (g) ÷ Molar mass (g/mol)) × Avogadro's number, we substitute the given values to derive the number of atoms. This yields 6.02 x 10^23 atoms, aligning with option a) 6.02 x 10^23 atoms.
13.
What is the mass in grams of 4.50 x 10^22 atoms of oxygen (O)? (Molar mass of oxygen is 16.00 g/mol)
Correct Answer
D. 1.44 x 10^-21 grams
Explanation
To ascertain the mass in grams of 4.50 x 10^22 atoms of oxygen, we integrate the molar mass of oxygen (16.00 g/mol) and Avogadro's number (6.022 x 10^23 atoms/mol). Employing the formula Mass (g) = Number of atoms × (Molar mass (g/mol) ÷ Avogadro's number), we substitute the provided values to compute the mass. This yields 1.44 x 10^-21 grams, corresponding to option d) 1.44 x 10^-21 grams.
14.
How many atoms are there in 2.00 g of chlorine (Cl)? (Molar mass of chlorine is 35.45 g/mol)
Correct Answer
B. 1.13 x 10^23 atoms
Explanation
Determining the number of atoms in 2.00 g of chlorine initiates by incorporating the molar mass of chlorine (35.45 g/mol) and Avogadro's number (6.022 x 10^23 atoms/mol). Utilizing the formula Number of atoms = (Mass (g) ÷ Molar mass (g/mol)) × Avogadro's number, we input the given values to calculate the number of atoms. Consequently, the result is 1.13 x 10^23 atoms, which aligns with option b) 1.13 x 10^23 atoms.
15.
What is the mass in grams of 4.20 x 10^23 atoms of sulfur (S)? (Molar mass of sulfur is 32.07 g/mol)
Correct Answer
B. 2.62 x 10^-20 grams
Explanation
To determine the mass in grams of 4.20 x 10^23 atoms of sulfur, we integrate the molar mass of sulfur (32.07 g/mol) and Avogadro's number (6.022 x 10^23 atoms/mol). Applying the formula Mass (g) = Number of atoms × (Molar mass (g/mol) ÷ Avogadro's number), we substitute the provided values to compute the mass. This yields 2.62 x 10^-20 grams, corresponding to option b) 2.62 x 10^-20 grams.