Formulae, Equations and Amount of Substance: แบบฝึกหัด

What is the volume, in \(\text{dm}^3\), occupied by \(0.44 \text{ g}\) of carbon dioxide gas, \(CO_2\), at room temperature and pressure (RTP)?
(Molar volume at RTP = \(24.0 \text{ dm}^3 \text{ mol}^{-1}\); Relative atomic masses: \(C = 12.0, O = 16.0\))

Calculate the total number of ions present in \(26.5 \text{ g}\) of anhydrous sodium carbonate, \(Na_2CO_3\).
(Molar mass: \(Na_2CO_3 = 106.0 \text{ g mol}^{-1}\); Avogadro constant \(L = 6.02 \times 10^{23} \text{ mol}^{-1}\))

A student added 10.0 \(cm^3\) of 1.00 \(mol \text{ dm}^{-3}\) hydrochloric acid to a 0.500 g sample of impure calcium carbonate. The excess acid required 4.00 \(cm^3\) of 0.500 \(mol \text{ dm}^{-3}\) sodium hydroxide for neutralisation.
Calculate the percentage purity of the calcium carbonate sample.

\(CaCO_3(s) + 2HCl(aq) \rightarrow CaCl_2(aq) + H_2O(l) + CO_2(g)\)

(Molar mass: \(CaCO_3 = 100.1 \text{ g mol}^{-1}\))

What is the percentage by mass of nitrogen in ammonium nitrate, \(NH_4NO_3\)?
(Relative atomic masses: \(H = 1.0, N = 14.0, O = 16.0\))

What is the maximum volume of carbon dioxide, in \(\text{dm}^3\), produced at room temperature and pressure (RTP) when \(2.40 \text{ g}\) of magnesium carbonate reacts completely with excess sulfuric acid?

\(MgCO_3(s) + H_2SO_4(aq) \rightarrow MgSO_4(aq) + CO_2(g) + H_2O(l)\)

(Molar volume at RTP = \(24.0 \text{ dm}^3 \text{ mol}^{-1}\); Molar mass: \(MgCO_3 = 84.3 \text{ g mol}^{-1}\))

State the molar volume, in \(\text{dm}^3 \text{ mol}^{-1}\), of any gas at room temperature and pressure (RTP).

Calculate the concentration, in \( \text{g dm}^{-3} \), of a solution prepared by dissolving 5.30 g of anhydrous sodium carbonate (\( \text{Na}_2\text{CO}_3 \)) in distilled water and making the total volume up to 250 \( \text{cm}^3 \).
(Molar mass: \( \text{Na}_2\text{CO}_3 = 106.0 \text{ g mol}^{-1} \))

A \(5.00 \text{ m}^3\) sample of air was found to contain \(15.0 \text{ mg}\) of sulfur dioxide, \(SO_2\). Calculate the concentration of sulfur dioxide in parts per million (ppm) by mass.
(Assume the density of air is \(1.20 \text{ kg m}^{-3}\))

A student heated 0.608 g of magnesium ribbon in a crucible until it reacted completely with oxygen in the air to form magnesium oxide, \(MgO\).

(a) Write a balanced chemical equation for this reaction, including state symbols. (1 point)
(b) Calculate the amount, in moles, of magnesium used. (1 point)
(c) Calculate the theoretical mass of magnesium oxide produced. (1 point)
(d) If 0.920 g of magnesium oxide was collected, calculate the percentage yield. (1 point)
(Relative atomic masses: \(Mg = 24.3, O = 16.0\))

When \(1.20 \text{ g}\) of a gaseous hydrocarbon Y is burned completely in excess oxygen, it produces \(3.77 \text{ g}\) of carbon dioxide and \(1.54 \text{ g}\) of water.

(a) Calculate the empirical formula of hydrocarbon Y. (3 points)
(b) At a temperature of \(373 \text{ K}\) and a pressure of \(101 \text{ kPa}\), \(0.500 \text{ g}\) of Y occupies a volume of \(274 \text{ cm}^3\). Calculate the molar mass of Y and determine its molecular formula. (3 points)
(c) Write a balanced chemical equation for the complete combustion of Y, including state symbols. (1 point)

(Relative atomic masses: \(C = 12.0\), \(H = 1.0\), \(O = 16.0\); Gas constant \(R = 8.31 \text{ J mol}^{-1} \text{ K}^{-1}\))