Chemical Formulae Equations And Calculations
Which word equation correctly represents the reaction between calcium carbonate and hydrochloric acid?
A student attempts to balance the equation H₂ + O₂ → H₂O by changing it to H₂ + O₂ → H₂O₂. State why this approach is incorrect. Which of the following identifies the error?
Calculate the relative formula mass (Mᵣ) of aluminium sulfate, Al₂(SO₄)₃. Aᵣ: Al = 27, S = 32, O = 16.
Calculate the amount, in moles, of 9.8 g of sulfuric acid (H₂SO₄). Aᵣ: H = 1, S = 32, O = 16.
What mass of sodium hydroxide (NaOH) is present in 0.60 mol? Aᵣ: Na = 23, O = 16, H = 1.
In the reaction 2Al(s) + 3Cl₂(g) → 2AlCl₃(s), what mass of aluminium chloride is produced when 5.4 g of aluminium reacts with excess chlorine? Aᵣ: Al = 27, Cl = 35.5.
A student calculated that 14.2 g of sodium sulfate should form in a reaction. The experiment produced 10.65 g. What is the percentage yield?
A compound contains 75.0% carbon and 25.0% hydrogen by mass. Determine its empirical formula. Aᵣ: C = 12, H = 1.
The empirical formula of a compound is CH₂O and its relative molecular mass is 180. What is its molecular formula?
Calculate the concentration, in mol dm⁻³, of a solution containing 0.050 mol of solute in 200 cm³ of solution.
Calculate the volume, in cm³, of carbon dioxide gas produced at rtp when 0.025 mol of hydrochloric acid reacts with excess calcium carbonate. CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂.
A solution of potassium hydroxide has a concentration of 0.15 mol dm⁻³. What volume, in cm³, is needed to provide 0.0060 mol of KOH?
In the practical determination of the formula of magnesium oxide by combustion, a student heats magnesium in a crucible with a lid. Which statement correctly explains why the lid is lifted periodically and then replaced?
A climber at high altitude boils water to dissolve a salt for a chemistry experiment. She measures 50.0 cm³ of the resulting 0.40 mol dm⁻³ solution and finds it reacts completely with 25.0 cm³ of barium chloride solution. The equation is: Na₂SO₄(aq) + BaCl₂(aq) → BaSO₄(s) + 2NaCl(aq). Calculate the concentration of the barium chloride solution in mol dm⁻³.
A student heats 3.69 g of hydrated magnesium sulfate, MgSO₄·xH₂O, until all water is removed. The anhydrous residue has a mass of 1.80 g. What is the value of x? Mᵣ: MgSO₄ = 120, H₂O = 18.
At room temperature and pressure, 4.8 dm³ of an unknown gas has a mass of 8.8 g. Calculate the relative molecular mass (Mᵣ) of the gas.
In a reduction experiment to determine the formula of a metal oxide, 3.18 g of copper(II) oxide was reduced by hydrogen gas. The mass of copper obtained was 2.54 g. A student claims the empirical formula is Cu₂O. Determine whether this claim is correct. Aᵣ: Cu = 64, O = 16.
A factory produces ammonia (NH₃) by reacting nitrogen with hydrogen: N₂ + 3H₂ → 2NH₃. In one batch, 56.0 g of nitrogen reacts with excess hydrogen. The theoretical yield of ammonia is calculated, but only 51.0 g of ammonia is obtained. Calculate the percentage yield. Aᵣ: N = 14, H = 1.
A student dissolves 4.0 g of sodium hydroxide (NaOH) in water to make 500 cm³ of solution. She then uses this solution to neutralise hydrochloric acid. Which value correctly gives the concentration of the NaOH solution? Aᵣ: Na = 23, O = 16, H = 1.
In the combustion experiment for magnesium oxide, a student records the following data: mass of crucible + lid = 25.00 g; mass of crucible + lid + magnesium = 25.48 g; mass of crucible + lid + product = 25.72 g. However, she forgot to replace the lid several times during heating. Which statement best describes the effect of this error on the calculated empirical formula?