1. Atomic Mass Of Chloroform
2. Atomic Mass Of Cl2

Molar mass of HCl = 36.46094 g/mol

This compound is also known as Hydrochloric Acid.

Convert grams HCl to moles or moles HCl to grams

Beware that isotopes are often written with just their mass number A. For example, chlorine with a mass of 37, may be written as chlorine-37, 37Cl, or Cl-37. Relative atomic mass Mass Spectrometer. The mass spectrometer is an instrument used to determine the relative atomic mass of an element. It can also show its isotopic composition.

• Would the atomic mass of Cl(35.453) round to the whole number 35 or 36? Does it really matter which one you choose?
• The mass of an electron is 9.1 × 10 –31 kg. Is 3.0 × 10 –25 J, calculate its wavelength. Q:-An element with mass number 81 contains 31.7% more neutrons as compared to protons. Assign the atomic symbol. Q:-How many neutrons and protons are there in the following nuclei? Q:-Complete the following chemical reactions.

But the relative atomic mass of chlorine is not 36. In any sample of chlorine, 75 per cent of the atoms are 35 Cl and the remaining 25 per cent are 37 Cl. Name: Chlorine Symbol: Cl Atomic Number: 17 Atomic Mass: 35.4527 amu Melting Point:-100.98 °C (172.17 K, -149.764 °F) Boiling Point:-34.6 °C (238.55 K, -30.279997 °F) Number of Protons/Electrons: 17 Number of Neutrons: 18 Classification: Halogen Crystal Structure: Orthorhombic Density @ 293 K: 3.214 g/cm 3 Color: green Atomic Structure.

Molecular weight calculation:
1.00794 + 35.453

In chemistry, the formula weight is a quantity computed by multiplying the atomic weight (in atomic mass units) of each element in a chemical formula by the number of atoms of that element present in the formula, then adding all of these products together.

The atomic weights used on this site come from NIST, the National Institute of Standards and Technology. We use the most common isotopes. This is how to calculate molar mass (average molecular weight), which is based on isotropically weighted averages. This is not the same as molecular mass, which is the mass of a single molecule of well-defined isotopes. For bulk stoichiometric calculations, we are usually determining molar mass, which may also be called standard atomic weight or average atomic mass.

Using the chemical formula of the compound and the periodic table of elements, we can add up the atomic weights and calculate molecular weight of the substance.

If the formula used in calculating molar mass is the molecular formula, the formula weight computed is the molecular weight. The percentage by weight of any atom or group of atoms in a compound can be computed by dividing the total weight of the atom (or group of atoms) in the formula by the formula weight and multiplying by 100.

Formula weights are especially useful in determining the relative weights of reagents and products in a chemical reaction. These relative weights computed from the chemical equation are sometimes called equation weights.

A common request on this site is to convert grams to moles. To complete this calculation, you have to know what substance you are trying to convert. The reason is that the molar mass of the substance affects the conversion. This site explains how to find molar mass.

Finding molar mass starts with units of grams per mole (g/mol). When calculating molecular weight of a chemical compound, it tells us how many grams are in one mole of that substance. The formula weight is simply the weight in atomic mass units of all the atoms in a given formula.

Imagine that you have a pile of rocks to move, and need to decide what equipment to rent so that you can move them. If the rocks are fairly small, you can get a shovel to pick them up. Larger rocks could be moved by hand, but big boulders will need some sort of mechanical scoop. The amount of each kind of rock will also determine how much time you will need to get the job done. Knowing the relative amounts of large, medium, and small rocks can be very useful in deciding how to approach the job.

Percent Natural Abundance

Most elements occur naturally as a mixture of two or more isotopes. The table below shows the naturally occuring isotopes of several elements, along with the percent natural abundance of each.

For some elements, one particular isotope predominates greatly over the other isotopes. Naturally occurring hydrogen is nearly all hydrogen-1 and naturally occurring oxygen is nearly all oxygen-16. For many other elements, however, more than one isotope may exist in more substantial quantities. Chlorine (atomic number 17) is a yellowish-green toxic gas. About three quarters of all chlorine atoms have 18 neutrons, giving those atoms a mass number of 35. About one quarter of all chlorine atoms have 20 neutrons, giving those atoms a mass number of 37. Were you to simply calculate the arithmetic average of the precise atomic masses, you would get 36.

[frac{left( 34.969 + 36.966 right)}{2} = 35.968 : text{amu}]

Clearly the actual average atomic mass from the last column of the table is significantly lower. Why? We need to take into account the percent natural abundance of each isotope in order to calculate what is called the weighted average. The atomic mass of an element is the weighted average of the atomic masses of the naturally occurring isotopes of that element. The sample problem below demonstrates how to calculate the atomic mass of chlorine.

Example (PageIndex{1})

Use the atomic masses of each of the two isotopes of chlorine along with the respective percent natural abundance to calculate the average atomic mass of chlorine.

Solution

Step 1: List the known and unknown quantities and plan the problem.

Known

• Chlorine-35: atomic mass (= 34.969 : text{amu}) and percent abundance (= 75.77%)
• Chlorine-37: atomic mass (= 36.966 : text{amu}) and percent abundance (= 24.23%)

Unknown

Atomic Mass Of Chloroform

• Average atomic mass of chlorine

Change each percent abundance into decimal form by dividing by 100. Multiply this value by the atomic mass of that isotope. Add together for each isotope to get the average atomic mass.

Step 2: Calculate.

[begin{array}{ll} text{chlorine-35} & 0.7577 times 34.969 = 26.50 : text{amu} text{chlorine-37} & 0.2423 times 36.966 = 8.957 : text{amu} text{average atomic mass} & 26.50 + 8.957 = 35.45 : text{amu} end{array}]

Atomic Mass Of Cl2

Note: Applying significant figure rules results in the (35.45 : text{amu}) result without excessive rounding error. In one step:

[left( 0.7577 times 34.969 right) + left(0.2423 times 36.966 right) = 35.45 : text{amu}]

Step 3: Think about your result.

The calculated average atomic mass is closer to 35 than to 37 because a greater percentage of naturally occurring chlorine atoms have the mass number of 35. It agrees with the value from the table above.

Summary

• The atomic mass of an element is the weighted average of the atomic masses of the naturally occurring isotopes of that element.
• Calculations of atomic mass use the percent abundance of each isotope.

Contributors and Attributions

• CK-12 Foundation by Sharon Bewick, Richard Parsons, Therese Forsythe, Shonna Robinson, and Jean Dupon.