How do you convert mass to amount in moles?

amount (mol) = mass (g) / molar mass (g mol-1).

How do you find the number of particles from an amount?

Number = amount (mol) x 6.02 x 10^23.

How many ions are in 0.100 mol of NaCl?

0.200 mol of ions, so 0.200 x 6.02 x 10^23 = 1.20 x 10^23 ions.

Write the equation for concentration in mol dm-3.

concentration = amount (mol) / volume (dm3).

How do you convert a concentration in mol dm-3 to g dm-3?

Multiply by the molar mass (g mol-1).

What is the concentration, in mol dm-3, of 0.0250 mol in 500 cm3?

0.0250 / 0.500 = 0.0500 mol dm-3.

State the four steps to find an empirical formula.

Masses or percentages, divide by Ar to get moles, divide by the smallest, multiply to whole numbers if needed.

How do you find the molecular formula from the empirical formula?

Divide the relative molecular mass by the empirical formula mass to get n, then multiply the empirical formula by n.

In combustion analysis, where does the carbon in a compound end up?

In the carbon dioxide: n(C) = n(CO2).

How do you find n(H) from the water produced in combustion?

n(H) = 2 x n(H2O), because each water molecule has two hydrogen atoms.

The mole, concentration and empirical formulaeEdexcel International A Level Chemistry: Flashcards

Card 1 of 130 of 13 known

Question

What is the Avogadro constant?

Tap or press Space to reveal

Tap card or press Space to flip

See all 13 cards

What is the Avogadro constant?: 6.02 x 10^23 mol-1, the number of particles in one mole.
How do you convert mass to amount in moles?: amount (mol) = mass (g) / molar mass (g mol-1).
How do you find the number of particles from an amount?: Number = amount (mol) x 6.02 x 10^23.
How many ions are in 0.100 mol of NaCl?: 0.200 mol of ions, so 0.200 x 6.02 x 10^23 = 1.20 x 10^23 ions.
Write the equation for concentration in mol dm-3.: concentration = amount (mol) / volume (dm3).
How do you convert cm3 to dm3?: Divide by 1000.
How do you convert a concentration in mol dm-3 to g dm-3?: Multiply by the molar mass (g mol-1).
What is the concentration, in mol dm-3, of 0.0250 mol in 500 cm3?: 0.0250 / 0.500 = 0.0500 mol dm-3.
State the four steps to find an empirical formula.: Masses or percentages, divide by Ar to get moles, divide by the smallest, multiply to whole numbers if needed.
Convert the mole ratio 1 : 1.5 to whole numbers.: Multiply by 2 to give 2 : 3.
How do you find the molecular formula from the empirical formula?: Divide the relative molecular mass by the empirical formula mass to get n, then multiply the empirical formula by n.
In combustion analysis, where does the carbon in a compound end up?: In the carbon dioxide: n(C) = n(CO2).
How do you find n(H) from the water produced in combustion?: n(H) = 2 x n(H2O), because each water molecule has two hydrogen atoms.

Exam questions on The mole, concentration and empirical formulae

A technician weighs 5.85 g of sodium chloride, NaCl (molar mass 58.5 g mol⁻¹), dissolves it in water and makes the solution up to 250 cm³. The Avogadro constant, L, is 6.02 × 10²³ mol⁻¹.
Calculate the concentration of the solution in mol dm⁻³ and in g dm⁻³.2 marks
A laboratory stock bottle holds 500 cm³ of sulfuric acid of concentration 0.250 mol dm⁻³. The molar mass of sulfuric acid, H₂SO₄, is 98.1 g mol⁻¹.
Calculate the mass of sulfuric acid needed to make 2.50 dm³ of solution of the same concentration.2 marks
A student analyses two compounds. Compound P, an oxide of iron, contains 2.10 g of iron and 0.90 g of oxygen. Compound Q is a hydrocarbon with relative molecular mass 70.0 that contains 85.7% carbon by mass. Relative atomic masses: H = 1.0, C = 12.0, O = 16.0, Fe = 55.8.
Use the data to calculate the empirical formula of compound P.3 marks

See the full worksheet

Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).