How To Convert Grams To Moles

Have you ever wondered How To Convert Grams To Moles? That might seem like a weird question, but it has crossed my mind before. I was reading an article about something scientific and they wanted to know how many grams were in 2 moles of magnesium.

Moles are a standard unit of measurement in chemistry that take into account the different elements in a chemical compound.^[1] Often, amounts of compounds are given in grams and need to be converted to moles. This conversion can help give you a clearer picture of the number of molecules you’re working with rather than dealing with weight, which can change between molecules. Although the conversion is simple, there are a number of important steps that need to be followed. Using this method, you can learn how to convert grams into moles.

Mole

A mole is the amount of substance of a system, which contains as many elementary entities as there are atoms in 0.012 kilogram (or 12 grams) of carbon-12, where the carbon-12 atoms are unbound, at rest and in their ground state.^[1] The number of atoms in 0.012 kilogram of carbon-12 is known as the Avogadro constant, and is determined empirically. The currently accepted value is 6.02214279(30)×10²³ mol^-1 (2007 CODATA).

According to the SI, the mole is not dimensionless, but has its very own dimension, namely “amount of substance”, comparable to other dimensions such as mass and luminous intensity.^[2] (By contrast, the SI specifically defines the radian and the steradian as special names for the dimensionless unit one.)^[3] The SI additionally defines the Avogadro constant as having the unit reciprocal mole, as it is the ratio of a dimensionless quantity and a quantity with the unit mole.^[3] However, if in the future the kilogram is redefined in terms of a specific number of carbon-12 atoms (see below), then the value of Avogadro’s number will be defined rather than measured, and the mole will cease to be a unit of physical significance.^[4]

The relationship of the atomic mass unit (u^[5]) to Avogadro’s number means that a mole can also be defined as: That quantity of a substance whose mass in grams is the same as its formula weight. For example, iron has a relative atomic mass of 55.845 u, so a mole of iron has a mass of 55.845 grams. This notation is very commonly used by chemists and physicists.

Scientists and engineers (chemical engineers in particular) sometimes measure amount of substance in units of gram-moles, kilogram-moles, pound-moles, or ounce-moles; these measure the quantity of a substance whose mass in grams, kilograms, pounds, or ounces (respectively) is equal to its formula weight. The SI mole is identical to the gram-mole.

Gram

A gram(g) is a metric unit of mass and was formally defined as the absolute weight of a volume of pure water equal to the cube of the hundredth part of a meter, and at the temperature of melting ice.

While a mole is the unit of measurement for amount of substance in the International System of Units.

A gram is a unit of mass in the metric system defined as one thousandth (1 x 10^-3) of a kilogram. Originally, the gram was defined as a unit equal to the mass of one cubic centimeter of pure water at 4°C (the temperature at which water has maximum density). The definition was changed when the base units for the International System of Units (SI) were redefined by the 26th General Conference of Weights and Measures. The change went into effect May 20, 2019.

The symbol for the gram is the lowercase letter “g.” Incorrect symbols include “gr” (the symbol for grains), “Gm” (the symbol for the gigameter), and “gm” (easily confused with the symbol for the gram-meter, g⋅m).

Gram may also be spelled gramme.

Key Takeaways: Gram Definition

• The gram is a unit of mass.
• One gram is one thousandth the mass of one kilogram. The previous definition of the gram was the absolute weight of a 1-centimeter cube of pure water at 4 °C.
• The symbol for the gram is g.
• The gram is a small unit of mass. It is approximately the mass of one small paper clip.

Examples of Gram Weight

Because a gram is a small unit of weight, its size may be difficult for many people to visualize. Here are common examples of objects that have about one gram of mass:

• A small paperclip
• A thumbtack
• A piece of chewing gum
• One US bill
• A pen cap
• One cubic centimeter (milliliter) of water
• A quarter teaspoon of sugar

Uses of the Gram

The gram is widely used in science, particular chemistry and physics. Outside of the United States, the gram is used to measure non-liquid cooking ingredients and produce (e.g., flour, sugar, bananas). Relative composition for food nutrition labels is stated per 100 grams of product, even within the United States

Part 1 Calculating the Molecular Mass

1. 1 Gather the necessary tools for solving a chemistry problem. Having everything you need easily accessible will simplify the process of solving the assigned problem. You will need the following:
   • A pencil and paper. Calculations are easier to solve when you write them out. Be sure to show all your steps to get full credit.
   • A periodic table. You will need to be able to find atomic weight of elements using the periodic table.
   • A calculator. Calculators are necessary to simplify calculations of complex numbers.
2. 2 Identify the elements in the compound that you need to convert into moles. The first step in calculating molecular mass is identifying each element that composes the compound. It is easy to distinguish elements because abbreviations contain only one or two letters.
   • If a compound is abbreviated with two letters, the first will be capitalized while the second will be lowercase. For example, Mg is the abbreviation for magnesium.
   • The compound NaHCO₃ has four elements in it: sodium (Na), hydrogen (H), carbon (C), and oxygen (O).
3. 3 Determine the number of atoms that each element contributes to the compound. You must know how many atoms of each element are present to calculate the molecular mass. ^[2] The number of atoms each element contributes will be written in a subscript next to the element.
   • For example, H₂O has two atoms of hydrogen and one atom of oxygen.
   • If a compound has parentheses followed by a subscript, each element within the parentheses gets multiplied by the number in the subscript. For example, (NH₄)₂S has two atoms of N, eight atoms of H, and one atom of S.
4. 4 Write down the atomic weight of each element. A periodic table is the easiest way to find the atomic weight of an element. Once you locate the element on the table, the atomic weight is usually found underneath the symbol for that element.
   • The atomic weight, or mass, or an element is given in atomic mass units (amu).^[3]
   • For example, the molecular weight of oxygen is 15.99.
5. 5 Calculate molecular mass. The molecular mass of a substance is calculated as the number of atoms of each element multiplied by the atomic weight of that element. ^[4] Knowing the molecular mass is necessary to convert grams to moles.
   • Multiply the number of atoms each element contributes to the compound by the atomic weight of that element.
   • Add the total weight of each element in the compound together.
   • For example, (NH₄)₂S has a molecular weight of (2 x 14.01) + (8 x 1.01) + (1 x 32.07) = 68.17 g/mol.
   • Molecular mass is also referred to as molar mass. ^[5]

Part 2 Converting Grams to Moles

1. 1 Set up the conversion formula. The number of moles you have of a compound can be calculated by dividing the number of grams of the compound by the molecular mass of the compound. ^[6]
   • The formula looks like this: moles = grams of compound/molar mass of compound
2. 2 Plug your numbers into the formula. Once you have properly set up the formula, the next step is just putting your calculations into the correct part of the formula. An easy way to check that you have everything in the right place is by the units. Canceling out all the units should leave you with just moles.
3. 3 Solve the equation. Using a calculator, divide the number of grams by the molar mass. The result is the number of moles in your element or compound.
   • For example, imagine you have 2 g of (NH₄)₂S and you want to convert it to moles. The molecular mass of (NH₄)₂S is 68.17g/mol. Divide 2 by 68.17, and you have 0.0293 moles of (NH₄)₂S.

Conclusion

People who have an understanding about the term conversion factor usually know that there are all types of factors that play a role in it. The factors include the value of the amount being converted, its country of origin and where it is being converted to.