Question

Using whole numbers, determine the molecular weight of calcium hydroxide, Ca(OH)₂.

a. 56

b. 57

c. 58

d. 74

Answer 1

The molecular weight of calcium hydroxide, Ca(OH)₂, is calculated by adding the atomic weights of calcium, oxygen, and hydrogen, which gives approximately 74.112 g/mol. Therefore, the correct answer, rounded to the nearest whole number, is 74.

The correct answer is :d.

Step-by-step explanation:

To determine the molecular weight of calcium hydroxide, Ca(OH)₂, we must calculate the sum of the atomic weights of all the atoms in the molecule. First, looking at the periodic table, we find the atomic weight of calcium (Ca) is approximately 40.08 g/mol. Each hydroxide group (OH) consists of oxygen (O) with an atomic weight of about 16.00 g/mol and hydrogen (H) with an atomic weight of 1.008 g/mol. Since there are two hydroxide groups in calcium hydroxide, we must take these into account twice.

• Atomic weight of Ca = 40.08 g/mol
• Atomic weight of O = 2 × 16.00 g/mol = 32.00 g/mol
• Atomic weight of H = 2 × (2 × 1.008) g/mol = 4.032 g/mol

Adding these together:

40.08 (Ca) + 32.00 (O) + 4.032 (H) = 74.112 g/mol

Therefore, the correct answer is 74, which is closest to this value when rounded to the nearest whole number.

The correct answer is :d.

Answer 2

The molecular weight of calcium hydroxide, Ca(OH)₂, is obtained by adding the atomic weights of one calcium atom, two oxygen atoms, and two hydrogen atoms, which gives a value of approximately 74.10 u. Hence, the closest whole number is 74.

Step-by-step explanation:

To determine the molecular weight of calcium hydroxide, Ca(OH)₂, we need to sum the atomic weights of all the atoms present in the formula. The atomic weight of calcium (Ca) is approximately 40.08 u, of oxygen (O) is about 16.00 u, and of hydrogen (H) is approximately 1.01 u. Calcium hydroxide has one calcium atom, two oxygen atoms, and two hydrogen atoms; therefore, the calculation is as follows:

• Calcium: 1 × 40.08 u = 40.08 u
• Oxygen: 2 × 16.00 u = 32.00 u
• Hydrogen: 2 × 1.01 u = 2.02 u

Adding these together yields:

40.08 u (calcium) + 32.00 u (oxygen) + 2.02 u (hydrogen) = 74.10 u

Therefore, the closest whole number to the molecular weight of calcium hydroxide is 74.