Chemical Formulae, Equations, the Mole and Gases

The first six ionisation energies of an element, M, in kJ mol⁻¹ are 660, 1267, 2218, 3313, 7863 and 9500. M forms its only chloride by heating M with chlorine. What is the equation for the formation of the chloride of M?

The relative abundances of all the isotopes present in a sample of nickel are shown.

What is the relative atomic mass of nickel calculated from these data?

The relative atomic mass of antimony, which consists of the isotopes ¹²¹Sb and ¹²³Sb, is 121.8. What is the percentage of ¹²³Sb in the isotopic mixture?

If there are n molecules in 10 g of methane, CH₄, how many molecules are in 55 g of carbon dioxide?

Which of the following statements about 20.3 g of Co₂(SO₄)₃ is false? [Molar mass = 406 g mol⁻¹]

Which of the following quantities is equal to the Avogadro constant?

Which substances contain the same number of atoms?

1 1.20 mol of NH₃
2 1.445 × 10²⁴ molecules of O₂
3 36.0 g of C₆H₁₂O₆
4 57.6 dm³ of Cl₂ at room temperature and pressure

Complete combustion of a sample of a hydrocarbon, Y, gave 0.66 g of carbon dioxide and 0.36 g of water. What is the empirical formula of Y?

A 2.0 g sample containing 0.0130 mol of an organoboron compound, with the formula C_xH_yBO_z, was burnt in an excess of oxygen. 4.58 g of CO₂ and 1.76 g of H₂O were produced. What is the molecular formula of the organoboron compound?

The empirical formula of an oxide of element X is X₂O₅. 106.5 g of X₂O₅ contains 60 g of oxygen. What is the identity of X?

Sodium hydrogencarbonate, NaHCO₃, can be prepared from sodium sulfide, Na₂S, by the following reactions.

Na₂S(s) + CaCO₃(s) → CaS(s) + Na₂CO₃(s)
Na₂CO₃(s) + H₂O(l) + CO₂(g) → 2NaHCO₃(s)

Assuming that the percentage yield in each step is identical, 20.5 kg of sodium hydrogencarbonate (M_r = 84.0) was formed from 50 kg of sodium sulfide (M_r = 78.1). What is the percentage yield of each step?

What is the volume of distilled water that must be added to 50 cm³ of 0.280 mol dm⁻³ KMnO₄ to dilute it to 0.160 mol dm⁻³?

Amedeo Avogadro discovered that equal volumes of gases at the same temperature and pressure contain the same number of molecules. Two closed containers, A and B, hold gases at the same temperature and pressure. The mass of gas A is equal to the mass of gas B, but gas A has a higher density than gas B. Which of the following statements is true?

Which graph is a correct representation of Boyle’s law?

0.0353 g of a sample of volatile organic compound was completely vaporised at 50 kPa and 300 K. The vapour occupied a volume of 40 cm³. On complete combustion in excess oxygen, 80 cm³ of carbon dioxide and 80 cm³ of water vapour were formed. All gaseous volumes were measured under identical conditions. What would be the molecular formula of the compound? (R = 8.31 J K⁻¹ mol⁻¹)

In an experiment, 0.100 g of a volatile liquid Q formed 0.0250 dm³ of vapour at 100 °C and 1 bar. What is the relative molecular mass of Q?

Deuterium, ²H, is an isotope of hydrogen. In an experiment, 18.0 g of gas A at 40 °C is found to occupy the same volume as 0.6 g of deuterium gas, ²H₂, at 20 °C. The pressure of gas A is twice that of the deuterium gas. What is the relative molecular mass of gas A?

A 20 dm³ vessel contains 0.25 mol of ammonia gas and a 30 dm³ vessel contains 0.42 mol of hydrogen chloride gas. When the two vessels were connected at 500 K, the following reaction occurs: NH₃(g) + HCl(g) → NH₄Cl(s). What is the resultant pressure, in Pa, in the combined vessel? (R = 8.31 J K⁻¹ mol⁻¹)

An equimolar mixture of H₂ and O₂ was placed in a sealed, rigid container at room temperature. The total pressure inside the container is P Pa. The mixture was sparked, and H₂ and O₂ reacted until H₂ was completely consumed. What is the partial pressure, in Pa, of O₂ in the container after the reaction at room temperature?

A gaseous sample containing x dm³ of gaseous methanol, CH₃OH, was burnt in 4x dm³ of oxygen to produce carbon dioxide and water vapour. The total pressure in the system after combustion was P. Which statements are correct?

1 Methanol reacts with oxygen in a 2 : 3 mole ratio.
2 The partial pressure of carbon dioxide in the system is 0.18P.
3 Assuming these gases behave ideally, they occupy an insignificant volume.

F₂(g) and Xe(g) are added to a container of fixed volume. The initial partial pressure of F₂(g) is 7.0 atm and that of Xe(g) is 1.6 atm. When all of the Xe(g) has reacted with F₂(g) to form a solid compound, C, the pressure of unreacted F₂(g) is 3.8 atm. The temperature remained constant throughout. What is the formula of the solid compound C?

Analysis of a mixture of sulfur-containing gases shows that hydrogen sulfide, H₂S, and carbon disulfide, CS₂, are present in a 2 : 1 mole ratio. The mixture is burned in excess oxygen, forming SO₂, CO₂ and H₂O. Which row describes the SO₂ : CO₂ mole ratio after complete combustion, and the relative deviation from ideal behaviour of the gases CO₂ and CS₂?