Quantitative Chemistry Click to start

Question 1 What is the mass in grams of one molecule of ethanoic acid CH3COOH? A 0.1 B 1 x 10-22 C 3.6 x 1025 D 60

Molar mass of CH3COOH is 24 + 4 + 32 = 60 Wrong Answer! Molar mass of CH3COOH is 24 + 4 + 32 = 60 Try Again

Question 2 A B C D Which is not a true statement? One mole of methane contains four moles of hydrogen atoms. B One mole of 12C has a mass of 12.00g. C One mole of hydrogen gas contains 6.02 x 1023 atoms of hydrogen. D One mole of methane contains 75% of carbon by mass.

Wrong Answer! 1 mole of hydrogen gas contain 6 x 1023 molecules of hydrogen gas. Since 1 mole of hydrogen is made up of 2 H atoms, 1 mole of hydrogen gas contains 2 x 6 x 1023 atoms. Try Again

Question 3 A B C D Which sample has the greatest mass? 1.0 mol N2H4 25.0 mol H2

Wrong Answer! Try Again A: 1 x (28+4) = 32g B: 2 x 28 = 56g C: 3 x (14+3) = 51g D: 25 x 2 = 50g Try Again

Question 4 Which one of the following statements about SO2 is/are correct? One mole of SO2 contains 1.8 x 1024 atoms One mole of SO2 has a mass of 64g A Both I and II B Neither I nor II C I only D II only

Wrong Answer! SO2 is made up of 3 atoms, hence 1 mole of SO2 contains 3 x 6 x 1023 atoms. Molar mass of SO2 = 32 + 32 = 64. Try Again

Question 5 A B C D 2Cl2 represents: two chlorine molecules two chlorine atoms C two chloride ions D four free chlorine atoms

Wrong Answer! 2Cl2 represents two chlorine molecules : Cl-Cl and Cl-Cl Try Again

Question 6 Which one of the following equations is not correctly balanced? A Ca(s)+2H+(aq) Ca 2+(aq)+H2 (g) B Mg(s)+ H2O(l) Mg(OH)2 (aq)+H2(g) C Fe 2+(aq)+Ag+(aq) Fe3+(aq)+ 2Cl-(aq) D Fe 2+(aq)+ Cl2 (g)  Fe3+(aq)+ 2Cl-(aq)

Wrong Answer! The charge is not balanced. Try Again

Question 7 Sulfuric acid and sodium hydroxide react together according to the equation? H2SO4(aq) + 2NaOH(aq)  Na2SO4(aq) + 2H2O(l) What volume of 0.250 moldm-3 NaOH is required to neutralise exactly 25.0 cm3 of 0.125 moldm-3 H2SO4 ? A 6.25 cm3 B 50 cm3 C 12.5 cm3 D 25.0 cm3

Wrong Answer! Try Again Conc x Vol of NaOH = 2 x Conc x Vol of H2SO4 0.25 x Vol of NaOH = 2 x 0.125 x 25 Vol of NaOH = 25 cm3 Try Again

Question 8 Which expression represents the density of a gas sample of relative molar mass, Mr, at temperature T, and pressure, P? A B C D

Wrong Answer! Try Again

Question 9 Separate samples of two gases, each containing a pure substance, are found to have the same density under the same conditions of temperature and pressure. Which statement about these two samples must be correct? A They have the same volume. B There are equal numbers of moles in the two samples. C They have the same relative molecular mass. D They condense at the same temperature.

Wrong Answer! Under the same pressure and temperature where R is a constant, they should have the same relative molecular mass. Try Again

Question 10 A 250 cm3 sample of an unknown gas has a mass of 1.42g at 350C and 0.85 atmospheres. Which expression gives its molar mass, Mr? (R = 82.05 cm3 atm K-1 mol-1) A B C D

Wrong Answer! Try Again

Question 11 What is the concentration of nitrate ions in 0.500cm3 of 0.60moldm-3 Fe(NO3)3 solution? A 0.60 moldm-3 B 0.90 moldm-3 C 1.20 moldm-3 D 1.80 moldm-3

Wrong Answer! Try Again Fe(NO3)3  Fe3+(aq) + 3NO3-(aq) Nitrate ions concentration = (0.6 x 3) = 1.80 moldm-3 Try Again

Question 12 32.0 grams of sulfur (atomic mass of 32.0) combine with a metal, M (atomic mass of 40.0) to give a product which weighs 52.0g. What is the empirical formula of the sulfide formed? A MS B MS2 C M2S D M2S5

Wrong Answer! Try Again Amount of M atoms = (52-32)/40 = 0.50 mol Amount of S atoms = 32/32 = 1.0 mol Multiplying through by 2 gives MS2 Try Again

Question 13 Under what conditions of temperature and pressure will a real gas behave most like an ideal gas? Temperature Pressure A Low Low B Low High C High High D High Low

Wrong Answer! High pressure will bring the gas molecules very close together. This causes more collisions and also allows the weaker attractive forces to operate. With low temperatures, the gas molecules do not have enough kinetic energy to continue on their path to avoid the attraction. Try Again

Question 14 At stp (i.e. 00C and 1 atm pressure (101 kPa)), it was found that 1.15 dm3 of a gas weighed 3.96g. What is its molar mass? A 77 gmol-1 B 47 gmol-1 C 39 gmol-1 D 4 gmol-1

Wrong Answer! Try Again

Question 15 A sample of argon gas in a sealed container of fixed value is heated from 50 to 2500C. Which quantity will remain constant? A Average speed of the atoms B Pressure of the gas C Average kinetic energy of the atoms D Density of the argon

Wrong Answer! All properties will increase in value except density which remain constant since the mass and volume of gas remain constant. Try Again

Question 16 Nitrogen(II) oxide,NO, is made from the oxidation of NH3: 4NH3 + 5O2  4NO + 6H2O An 8.5g sample of NH3 gives 15.0g of NO. What is the percentage yield of NO? A 40% B 60% C 80% D 100%

Wrong Answer! Try Again Amount of NH3 = 8.5/17 = 0.5 mol Amount of NO = 15/30 = 0.5 mol Percentage yield = 0.5/0.5 x 100% = 100% Try Again

Question 17 A pure compound contains 24g of carbon, 4g of hydrogen and 32g of oxygen. No other elements are present. What is the empirical formula of the compound? A C2H4O2 B CH2O C CH4O D CHO

Wrong Answer! Try Again No. of moles of C = 24/12 = 2 No. of moles of H = 4/1 = 4 No. of moles of O = 32/16 = 2 Dividing all by 2 gives a ratio of C:H:O = 1:2:1 The empircal formula is CH2O Try Again

Question 18 1000cm3 of ammonia gas combines with 1250cm3 of oxygen to produce two gaseous compounds with a combined volume of 2500cm3, all volumes being measured at 2000C and 0.500 atm pressure. Which of the following equations fits the facts? A 4NH3 + 7O2  4NO2 + 6H2O B 4NH3 + 5O2  4NO + 6H2O C 4NH3 + 5O2  4N2O2 + 6H2O D 4NH3 + 3O2  2N2+ 6H2O

Wrong Answer! Try Again 4 vol + 5 vol  10 vol Experimental data 1 vol + 1.25 vol  2.5 mol Multiplying throughout by 4 gives 4 vol + 5 vol  10 vol Try Again

Question 19 A B C D Butane burns in oxygen according to the equation 2C4H10(g) + 13O2(g)  8CO2(g) + 10H2O(g) If 11.6g of butane is burned in 11.6g of oxygen which is the limiting reagent? A Neither B Butane C Oxygen D Oxygen and butane

Wrong Answer! Try Again No. of moles of butane = 11.6/58 = 0.2 No. of moles of oxygen = 11.6/32 = 0.3625 2 mols of butane react with 13 mols of oxygen 0.2 mols of butane will react with 1.3 mols of oxygen. 0.3625 mols of oxygen will react with 0.05577 mols butane. The limiting reagent is oxygen since the no. of mols of butane produced by 0.3625 mols is smaller. Try Again

Question 20 A 350cm3 sample of helium gas is collected at 22.00C and 99.3kPa. What volume would this gas occupy? A 318cm3 B 450cm3 C 477cm3 D 220cm3

Wrong Answer! Try Again

Question 21 When 250 cm3 of 3.00 moldm-3 HCl(aq) is added to 350 cm3 of 2.00 moldm-3 HCl(aq) the concentration of the solution of hydrochloric acid obtained in moldm-3 is: A 1.45 B 2.90 C 2.50 D 2.42

Wrong Answer! Try Again (250+350)/1000 x Conc of HCl = 250/1000 x 3 + 350/1000 x 2 Conc of HCl = (0.25 x 3 + 0.35 x 2)/0.6 = 2.416moldm-3 Try Again

Question 22 Magnesium reacts with hydrochloric acid according to the following equation: Mg(s) + 2HCl(aq)  MgCl2(aq) + H2(g) What mass of hydrogen will be obtained if 100 cm3 of 2.00 moldm-3 HCl are added to 4.86g of magnesium? A 2.0g B 0.8g C 0.4g D 0.2g

Wrong Answer! Try Again No. of moles of HCl = 100/1000 x 2 = 0.2 No. of moles of Mg = 4.86/24 = 0.2025 The limiting reagent is HCl Since 2 mols of HCl produces 1 mol H2, 0.2 mols of HCl produces 0.1 mol H2. Hence, 0.1 x 2g = 0.2g of H2 Try Again

Question 23 12g of anhydrous magnesium sulfate combines with 12.6g of water to form hydrated manesium sulfate. What is the formula of the hydrated magnesium sulfate? A MgSO4.9H2O B MgSO4.7H2O C MgSO4.5H2O D MgSO4.3H2O

Wrong Answer! Try Again No. of moles of MgSO4 = 12/122 = 0.09836 No. of moles of H2O = 12.6/18 = 0.7 Multiplying by 10 to both gives approximately 1 mole MgSO4 and 7 moles H2O Try Again

Question 24 In order to dilute 40.0 cm3 of 0.600 moldm-3 HCl(aq) to 0.100 moldm-3, what volume of water must be added? A 60 cm3 B 160 cm3 C 200 cm3 D 240 cm3

Wrong Answer! Try Again M1V1= M2V2 0.600moldm-3 x 40.0cm3 = 0.600moldm-3 x V2 V2 = 240cm3 V2 – V1 = 240 – 40 = 200 cm3 Try Again

Congratulations!