# Oxygen and Excess Reagent

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• Published : November 28, 2012

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non-metals plus O2 form non-metal oxides

Non metal oxides plus water form oxy acids

Metals combine with oxygen to form metal oxides

Metal carbonates decompose to metal oxides and CO2

Active metals plus acid give hydrogen gas and the metal salt of the acid

Metal oxides plus water combine to form metal hydroxides

A metal oxide plus acid yields a salt water

to write a net ionic equation you first require a balanced molecular equation. We next ‘tear apart’ any compound that is listed as aqueous, into their constituent ions. And finally we cross off any ion that appears (in exactly the same form) on both sides of the equation. These are known as spectator ions and do not do anything in the reaction we are interested in.

Eg.2 BaCl2 (aq) + K2SO4(aq) = BaSo4(s) + 2KCl(aq)
Ba 2+(aq) + SO4 2-(aq) = BaSO4 (s)

Eg.3 HC2H3O2(a) + NaHCO3(a) = NaC2H3O2 (a) + H2CO3(a) (H2O + CO2) HC2H3O(a) + HCO-3(a) == C2H3O2 (a) = H2O(l) +co2(a)

Eg.4 Cl2(a) +2 KI(a) == 2KCl(a) + I1(g)
Cl2(a) + 2I(a) ==2Cl-(a) + I2(g)

Atomic Mass conversions ( mass to moles and moles to mass)

(do not round molar masses)

How different elements react with your oxygen.

The Net Ionic equations

The molar mass of any compound can be calculated from the sum of the masses of all of the elements in the compounds.

Mole to mole conversions

In a balanced chemical reaction such as:

3H2(g) + N2(g) == 2NH3(g)

it can be said that it takes 3 moles of hydrogen and one mole of nitrogen to produce two moles of ammonia. This balance ( or equality) enables us to convert from one compound to another. If we had 6 moles of H2(g).

a)How many moles of NH3(g) would it produce?

b)How many moles of N2(g) would be required to react perfectly with the hydrogen?

a)6 Moles H2(g) x 2 mol3es NH=4Moles NH3(g)

3 moles H2

b) 6 moles H2x 1 mole N2

3 moles H2 === 2mol N2

Eg1. Copper metal can be used to extract silver from silver nitrate solution according to the following balanced equation (stage 1). What mass of silver is produced from 5.00g of copper metal and excess silver nitrate solution?

2AgNO3(a) + Cu(s) == 2Ag(s) + Cu(NO3)2(a)

Stage 2- using the balanced equation to identify mole ratios

Relevant ratio= Cu:Ag = 1 mole Cu: 2 moles Ag

Stage 3- apply this to the problem given

Mass of Cu ->Moles of Cu -> Moles of Ag -> Mass of Ag

5.00gx1 mole Cu x 2 moles Ag x 107.87Ag ==

63.55gCu x 1 mole Cu 1 mole Ag 17.0g Ag

Note: include units to show how they cancel and give correct units for required answer (in this case, grams of silver).ver).

Eg2. what mass of carbon dioxide is produced by the complete combustion of 20.00g Propane gas ( use above equation)?

Equation: C3H8(g) + 5O2(g) ⋄ 3CO2(g) + 2H2O9(l)

Relevant mole ratio: 1mol C3H8 : 3CO2(g)

20.00g C3H8 x 1 mol C3H8 x 3 molCO2 x 44.01g

44.094g 1 mol c3h8 1 molCO2

59.89 g of co2

Tuesday September 18th. (all on black board)

In a chemical calculation, to find limiting reagent, calculate yield that could be formed in each case.

Determine limiting reagent:

Smaller mass of CO2 from calculation using CaCO3

CaCO3 is therefore the limiting reagent

HNO3 is therefore the excess reagent.

Calculating excess reagent on exam

Percentage yield= actual yield x 100%

theoretical yield

Mass conversions for compounds

Mass to mass conversions

Continued….

59.89 g of co2