The Mole & the Avogadro Constant (Cambridge (CIE) AS Chemistry): Exam Questions

5.0 g of an unknown Group 2 nitrate was decomposed to produce 0.0843 mol of gas.

2X(NO₃)₂ (s) → 2XO (s) + 4NO₂ (g) + O₂ (g)

i) Calculate the amount, in mol, of the unknown Group 2 nitrate.

[1]

ii) Calculate the number of ions in 0.03372 mol of the unknown Group 2 nitrate.

[2]

Identify the unknown element X.

Using your answer to part (b), calculate the mass, in grams, of the metal oxide produced in the complete decomposition of 0.03372 mol of X(NO₃)₂.

Give your answer to 3 significant figures.

State whether strontium nitrate would need to be heated more or less strongly than X(NO₃)₂ to decompose. Explain you answer.

Barium sulfate is a white insoluble solid and is used in stomach X-rays and as a pigment for paint.

Calculate the number of particles in 74 mg of barium sulfate.

State the ionic equation for the formation of barium sulfate.

A different barium compound, barium carbonate, was reacted with hydrochloric acid. 

i) Write the balanced symbol equation for this reaction.

[1]

ii) 0.03 moles of carbon dioxide were formed in this reaction. Calculate the number of hydrogen ions that reacted.

[2]

When magnesium reacts with hydrochloric acid, the following reaction occurs:

Mg (s) + 2HCl (aq) → MgCl₂ (aq) + H₂ (g)

During the reaction, the hydrogen produced occupies 103 cm³ at 25.0 °C and 100 kPa.

Calculate the amount, in moles, of hydrogen gas produced during the reaction.

A student completed the same reaction as in part (a), using 3.75 g of magnesium.

Calculate the mass, in grams, of magnesium chloride produced by the student during this reaction. Give your answer to 3 significant figures.

Calculate the number of hydrogen atoms produced during the student's reaction in part (b).