How Much? The Amount of Chemical Change (HL IB Chemistry)

A 2.27 dm³ sample of nitrogen gas, measured under standard conditions, reacted with a large excess volume of hydrogen gas to produce ammonia. Only 20.0% of the nitrogen gas reacted to produce ammonia.

What mass of ammonia was made?

Excess aqueous cold sodium hydroxide is reacted with 0.10 mol of chlorine gas, Cl₂. One of the products is a compound of sodium, oxygen and chlorine.

What mass of the product is formed?

When heated, anhydrous magnesium nitrate, Mg(NO₃)₂, will decompose into magnesium oxide and a mixture of gases shown in the following equation

2Mg(NO₃)₂ (s) → 2MgO (s) + 4NO₂ (g) + O₂ (g)

1.48 g of anhydrous magnesium nitrate is heated until no further reaction takes place.

What mass of nitrogen dioxide is produced?

A hydrocarbon, X, was burned in excess oxygen to give carbon dioxide and water as the only products. 0.1mol of X produced 9.08dm³ of carbon dioxide at standard conditions.

What is the molecular formula of X?

A Group II metal of mass 0.33 g reacted with 606.9 cm³ of oxygen at 273 K and 100 kPa pressure, to form an oxide which contains O^2– ions.

What is the molar mass of the metal?

Solid fertilisers often contain the elements N, P and K in a ratio of 20 g : 30 g : 10 g per 100 g of fertiliser. It is recommended that the fertiliser is used at 14 g of fertiliser per 5 dm³ of water.

What is the concentration of nitrogen atoms in the solution?

When lead sulfide reacts with oxygen it produces lead(II) oxide and sulfur dioxide according to the equation below:

PbS (s) + O₂ (g) → PbO (s) + SO₂ (g)

What is the whole number sum of the coefficients in the balanced equation?

Some coal contains as much as 3% sulfur.

How much sulfur dioxide (M_r = 64.07 g mol^-1) is produced by burning a lump of coal of mass 125 g?  (A_r S = 32.07)

The conversion of toxic emissions into harmless products takes place in catalytic converters as follows:

_CO (g) + _NO (g) → _CO₂ (aq) + _N₂ (g)

The sum of the coefficients is

A compound is made of sulfur and oxygen only. A sample of the compound has a mass of 8.0 g and consists of 3.2 g of sulfur and 4.8 g of oxygen.

What is the empirical formula?

(RAMs  S = 32.0, O = 16.0)

Which of the following samples has the largest mass?

(RAMs, H = 1.01, N = 14.01, O = 16.00)

Natural gas contains on average 5.5 mg / m³ of sulfur in the form of hydrogen sulfide, H₂S (M_r = 34.09).

If a typical household in the UK consumes 0.198 m³ of gas per day, what is the average annual emission of sulfur in g per household?

The coefficient for copper when the following equation is balanced is:

_Cu   +  _HNO₃   →  _Cu(NO₃)₂   + _NO   +   _H₂O

Excess dilute hydrochloric acid is added separately to equal masses of the four metals, calcium, zinc, magnesium and strontium. Which metal will give off the largest volume of hydrogen gas in the reaction?

When a 1.00 g sample of carbon is burned in a limited supply of oxygen, 0.72 g of the carbon combusts to form CO₂ and 0.28 g of the carbon combusts to form CO_.

These gases were passed through excess NaOH (aq) which absorbs the CO₂, but not the CO. The remaining gas was then dried and collected.

Assuming that all gas volumes were taken at 273.15 K and 100 kPa pressure, what was the volume of gas at the end of the reaction? (Molar volume of a gas at STP = 22.7 dm³ mol^-1)

Chicken eggs are made up of 5% by mass of egg shell. The average egg has a mass of 50 g.

Assume that chicken eggshell is pure calcium carbonate. 

How many complete chicken’s egg shells would need to neutralise 50 cm³ of 2.0 mol dm^-3 ethanoic acid?

When a sample of potassium oxide, K₂O, is dissolved in 250 cm³ of distilled water, 25 cm³ of this solution is titrated against sulfuric acid with a concentration of 2.00 mol dm^-3. Complete neutralisation takes place with 15 cm³ of sulfuric acid.

What is the mass of the original sample of potassium oxide dissolved in 250 cm³ of distilled water?

Iron and chromium can be made into an alloy called ferrochrome. Ferrochrome can be dissolved in dilute sulfuric acid to produce FeSO₄ and Cr₂(SO₄)₃. The FeSO₄ reacts with acidified K₂Cr₂O₇ as shown in this equation:

14H⁺ + 6Fe²⁺ + Cr₂O₇^2- → 2Cr³⁺ + 6Fe³⁺ + 7H₂O

When 1.00 g of ferrochrome is dissolved in dilute sulfuric acid and then titrated, 13.1 cm³ of 0.100 mol dm^-3 K₂Cr₂O⁷ is needed for the complete reaction.

In the sample of ferrochrome, what is the percentage by mass of Fe?

Some fireworks can use the reaction between aluminium powder and anhydrous barium nitrate as a propellant. Metal oxides and nitrogen are the only products when this happens.

10Al + 3Ba(NO₃)₂ → 5Al₂O₃ + 3BaO + 3N₂

When 0.783 g of anhydrous barium nitrate (M_r 261.35) reacts with an excess of aluminium what is the volume of nitrogen produced in cm³?
(Molar volume of a gas at stp = 22.7 dm³)

Excess acidified potassium dichromate(VI) was mixed with 2.76 g of ethanol. The reaction mixture was then boiled under reflux for one hour. Once the reaction had completed, the organic product was collected by distillation.

The yield of the product was 75.0%

What is the mass of the product collected?

The concentration of calcium ions in a sample of water can be determined by using an ion-exchange column, shown in the diagram below:

 A 50 cm³ sample of water containing dissolved calcium sulfate was passed through the ion-exchange resin.

Each calcium ion in the sample was exchanged for two hydrogen ions. The resulting acidic solution collected in the flask required 25 cm³ of 1.0 x 10^-2 mol dm^-3 potassium hydroxide for complete neutralisation.

What was the concentration of the calcium sulfate in the original sample?