Quantitative Chemistry

Given the reaction 3FeCl2+2Na3PO4→Fe3(PO4)2+6NaCl, if you start with 23g of FeCl2 (molar mass 127 g/mol) and 41g of Na3PO4 (molar mass 164 g/mol), what are the initial moles of each reactant?

0.18 mol of FeCl2 and 0.25 mol of Na3PO4.

What is the definition of stoichiometry?

Stoichiometry is a way of calculating how much of something will be made or how much stuff will be needed to make something.

For the reaction N2+3H2→2NH3, if 6 moles of N2 react, how many moles of H2 are needed and how many moles of NH3 are produced?

18 moles of H2 are needed and 12 moles of NH3 are produced.

In chemistry, the number of _____ of a substance can be calculated by dividing its ____ by its molar mass (Mr).

moles, mass

What is the primary use of stoichiometry in chemistry?

Stoichiometry is used to determine the moles or mass of a substance needed or formed during a chemical reaction.

Stoichiometry is a method used to determine _______ amounts from _____ amounts in chemical reactions.

Unknown, known

How much O2 (in moles) is produced when 1.5 mol of KClO3 decomposes according to the reaction 2KClO3→2KCl+3O2?

2.25 mol of O2

If 0.25 moles of N2 react completely in the reaction N2+3H2→2NH3, what are the moles of H2 consumed and NH3 produced?

0.75 moles of H2 are consumed, and 0.5 moles of NH3 are produced.

What is the mass of 2.25 moles of O2?

72g

In the reaction 3FeCl2+2Na3PO4→Fe3(PO4)2+6NaCl, if FeCl2 is the limiting reagent with 0.18 mol, how many moles of NaCl can be formed?

0.36 mol

The ____________ of chemicals in a balanced ________ provide the relative amounts (in mol) of _________ and ________, which is known as the _____ ratio.

Coefficients, equation, reactants, products, molar

For the reaction 3FeCl2+2Na3PO4→Fe3(PO4)2+6NaCl, if you have 0.18 mol of FeCl2 and 0.25 mol of Na3PO4, which reactant is the limiting reagent?

FeCl2

To produce 100g of KCl from the decomposition of KClO3 (where Mr of KClO3 = 122.5), how much KClO3 in grams is needed? The balanced equation is: 2KClO3→2KCl+3O2.

164.15g

If 1.5 mol of KClO3 decomposes according to the reaction 2KClO3→2KCl+3O2, how many moles of O2 are produced?

2.25 mol of O2 are produced.

What is the balanced chemical equation for the reaction where 0.8g of methane reacts with 3.2g of oxygen to form 2.2g of carbon dioxide and 1.8g of water?

CH4+2O2→CO2+2H2O

T/F: During a chemical reaction, atoms are created or destroyed.

False

Define percentage yield.

A way of calculating what percentage of the expected amount of product did you actually get.

What is the formula to calculate percentage yield?

mass of product actually made (g) / maximum expected amount of product (g) * 100

What does a percentage yield of 0% or 100% mean?

0% percentage yield means no reactants were converted to product. 100% percentage yield means all reactants were converted to product.

Why will percentage yield never be 100%? (3)

•If a reaction is reversible, the reactants will never completely be converted into product - reaction goes both ways. Products always reacting to change to original reactants - lower yield.

•When a liquid is filtered to remove solid particles, always some liquid / solid is lost. If liquid wants to be kept, some liquid lost with filter paper. If solid wants to be kept, it can be scraped off the filter paper.

•Unexpected reactions may be happening on the side. Gases can react from air, impurities in mixture - lower yield.

Define atom economy.

It tells you what percentage of the mass of the reactants ends up as useful products when manufacturing a chemical.

What is the formula for atom economy?

atom economy (%) = Mr of desired products / Mr of all reactants * 100

Which reactions always have an atom economy of 100%?

All atoms in reactants have been converted into useful products.

What are the economic advantages of a high atom economy? (3)

•It needs less reactants to produce the desired amount of product/s.

•Less waste products produced, so less money spent on waste removal / disposal

•Profitable

What are the environmental advantages of a high atom economy? (3)

•Uses fewer raw materials; it ensures that finite resources last as long as possible.

•Produces less waste - good for environment; waste chemicals often harmful and difficult to dispose.

•Tends to be more sustainable.

1 litre is equal to how many dm^3?

1

What is the equation for volume (dm^3) in terms of molar gas volume? Rearrange it to give two more forms of it.

•volume (dm^3) = 24 * moles

•volume (dm^3) / moles = 24

•moles = volume (dm^3) / 24

What is the equation for volume (cm^3) in terms of molar gas volume? Rearrange it to give two more forms of it.

•volume (cm^3) =- 24000 * moles

•volume (cm^3) / moles = 24000

•moles = volume (cm^3) / 24000

What is the equation for concentration through mass? Rearrange it to give two more forms of it.

•concentration = mass / volume

•mass = volume * concentration

•volume = mass / concentration

Define concentration.

The amount of solute dissolved in a volume of solvent.

What is the equation for concentration through moles? Rearrange it to give two more forms of it

•concentration (mol/dm^3) = moles / volume (dm^3)

•moles = volume (dm^3) * concentration (mol/dm^3)

•volume (dm^3) = moles / concentration (mol/dm^3)

How do you convert between g/dm^3 and mol/dm^3?

•g/dm^3 to mol/dm^3: multiply by Mr of chemical

•mol/dm^3 to g/dm^3: divide by Mr of chemical

Define titration.

A way to measure volumes precisely

Define the end point.

The point at which the acid and alkali have reacted completely.

How is the end point shown?

Using an indicator.

What are concordant titres?

Titres within 0.1cm^3 of each other

What are titres?

Volume in titration.

What is a biurette?

A piece of equipment to measure a variable volume of up to 2dp.

What is a volumetric pipette?

A piece of equipment that measures a fixed volume.