1.2 Amount Of Substance

What is the definition of parts per million (ppm)?

1 ppm is defined as a mass of 1 mg dissolved in 1 dm^3 of water, or 10^-3 g in 10^3 g, which is the same as saying the concentration is 1 in 10^6 or 1 in a million.

What are standard temperature and pressure values?

273 K / 0 C and 101.3 kPa respectively.

What are some factors that could lead to a percentage yield greater than 100%?

A percentage yield greater than 100% could be due to the crystals still being dry when weighed, impurities in the crystals, or the mass of the filter paper or container being mistakenly included in the total mass of the product.

What is the equation for calculating atom economy?

Atom economy = (molecular mass of desired product / sum of molecular masses of all reactants) x 100.

What is the definition of atom economy?

Atom economy is a measure of the efficiency of a chemical reaction in terms of the amount of atoms of the reactants that end up in the desired product.

How is atom economy calculated?

Atom economy is found directly from the balanced equation by calculating the molecular mass of the desired product divided by the sum of molecular masses of all reactants, then multiplied by 100.

What is the significance of atom economy in chemical reactions?

Atom economy is significant because it shows how efficiently a reaction uses its starting materials to produce the desired product.

What is atom economy?

Atom economy shows how many of the atoms used in a reaction become the desired product, and the rest of the atoms or mass is wasted.

What is Avogadro's constant?

Avogadro's constant is a proportionality constant that relates the number of particles in a substance to the amount of substance in moles.

What can chemical equations be used to calculate?

Chemical equations can be used to calculate the moles or masses of reactants and products.

What is the definition of concentration?

Concentration can be defined as the amount of a substance dissolved in a quantity of liquid.

What is the formula to calculate concentration in ppm for atmospheric gas concentration?

Concentration in ppm = volume of gas × 1000000 / volume of air.

How do you calculate the molar mass of a gas?

Divide the mass of the gas by the number of moles of the gas.

What are real gases?

Gases that do not fit the description of ideal gases exactly but may come very close are called real gases.

What are ideal gases?

Gases that follow the kinetic theory of gases are called ideal gases.

What is the meaning of ppmv?

It shows that the value relates to concentration by volume.

What is the equation to calculate mass concentration?

Mass concentration in g dm^-3 = mass of solute in g / volume of solution in dm^3.

What is the equation to calculate molar concentration?

Molar concentration in mol dm^-3 = number of moles (or amount) / volume of solution in dm^3.

What is the molar mass?

Molar mass is the mass per mole of a substance in g mol^-1.

What is the unit of measurement for amount of substance?

Moles (mol).

What is the formula for calculating moles using concentration and volume?

Moles, n = concentration x volume.

What is the formula for calculating moles using mass and molar mass?

Moles, n = mass, m / molar mass, M.

What is the equation to calculate the number of moles?

Number of moles (or amount) = mass / molar mass.

What is the equation to calculate the number of moles for any volume of gas?

Number of moles = Volume of gas (dm^3) / Molar gas volume (dm^3).

What is the formula to calculate the number of moles of a substance in a solution?

Number of moles of a substance = volume of solution (in dm^3) x molar concentration in mol dm^-3.

What factors can affect the percentage yield in a reaction?

Other reactions taking place simultaneously, the reaction not going to completion, and products being lost during separation and purification can affect the percentage yield in a reaction.

What is percentage yield?

Percentage yield shows how much of a particular product you get from the reactants compared to the maximum theoretical amount that you can get.

What is the difference between qualitative and quantitative atom economy?

Qualitative atom economy refers to a comparison of the atom efficiency of different reactions, while quantitative atom economy involves calculating the actual percentage of atoms that end up in the desired product.

Why is it important to show your working when calculating atom economy?

Sometimes a question may ask you to show your working, even if the atom economy is obvious, to ensure that you understand the concept and can apply it correctly.

What is the actual yield in a reaction?

The actual yield is the number of moles or mass of product obtained experimentally.

What is the atom economy of addition reactions?

The atom economy of addition reactions is always 100% because all of the atoms are used to make the desired product.

What are the common calculations for amount of substance?

The common calculations for amount of substance include moles = mass / molar mass, moles = concentration x volume, and moles = number of particles / Avogadro's constant.

What is the equation used to calculate the number of moles for an unknown gas?

The ideal gas equation.

What is the kinetic theory of gases?

The kinetic theory of gases states that molecules in gases are constantly moving, and makes assumptions that gas molecules are moving very fast and randomly, hardly have any volume, do not attract or repel each other, and no kinetic energy is lost when the gas molecules collide with each other.

What is the molar mass of a gas?

The molar mass of a gas is the mass of one mole of the gas, usually expressed in grams per mole (g/mol).

What is the next step after determining the moles of substances in a chemical equation?

The next step after determining the moles of substances in a chemical equation is to identify the ratio between the substances using the balanced chemical equation.

What is the definition of amount of substance?

The number of particles in a substance, measured in moles.

What are reacting volume calculations commonly associated with?

The reactions of gases.

What can be determined by calculating gas volumes using number of moles calculations?

The size of the equipment that you use in an experiment.

What is the relationship between temperature and the average kinetic energy of gas molecules?

The temperature of the gas is related to the average kinetic energy of the molecules.

What is the theoretical yield in a reaction?

The theoretical yield is the number of moles or mass obtained by a reacting mass calculation.

What are the units for molar concentration?

The units for molar concentration are mol dm^-3.

How can atom economy be calculated using mass?

To calculate atom economy using mass, divide the mass of the desired product formed by the total mass of all reactants, and then multiply by 100.

What is the equation to calculate the concentration of a gas in ppm?

concentration in ppm = volume of gas × 1000000 / volume of air.

What is the formula to calculate the number of moles of gas?

n = PV/RT.

What is the formula for calculating percentage yield?

percentage yield = actual yield / theoretical yield x 100.