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Dodaj cały arkusz do zestawuHydrogen peroxide has the molecular formula H2O2. Which statement about this formula is correct? A. It shows that the two oxygen atoms are joined by a double bond B. It is the same as the empirical formula of hydrogen peroxide C. It shows that one mole…
Magnesium ribbon of known mass was heated strongly in a crucible, and the heating was repeated until the mass no longer changed. The final mass of the solid was then recorded. Assume that magnesium oxide is the only product. Which of the following can be…
A gas sample gave the experimental results below. Which expression gives the molar mass of the gas, in g mol−1? Ideal gas constant R = 8.31 J K−1 mol−1, PV = nRT A. B.…
What is the maximum number of electrons that can occupy the main energy level n = 3? A. 6 B. 9 C. 18 D. 32
Which statement best explains why the first ionization energy of aluminium is lower than that of magnesium? A. Aluminium has more protons than magnesium B. Aluminium has a smaller atomic radius than magnesium C. The outer electron of aluminium is in a 3p…
Which of the following statements can be deduced from the period in which an element is placed? I. The number of occupied main energy levels II. The number of protons in the nucleus III. The number of electrons in the outer energy level A. I only B. I and II…
The unbalanced equation below shows an oxide of an element X reacting with water. + H2O → H2XO4 Which of these oxides could be the missing reactant? A. Na2O B. SO2 C. P4O10 D. SO3
Which ion has an incomplete d sub-level? A. Cu2+ B. Zn2+ C. Ca2+ D. Sc3+
Four solids, P, Q, R and S, were tested. The results are shown in the table. Which solid most likely has an ionic lattice structure? A. P B. Q C. R D. S
Magnesium has a higher melting point than sodium. Which statement best explains this? A. Magnesium atoms have a greater relative atomic mass than sodium atoms B. Magnesium has a lower first ionization energy than sodium C. Magnesium ions have a larger radius…
In which species does the central atom have fewer than eight valence electrons? A. AlCl3 B. CCl4 C. NH4+ D. H3O+
The Lewis formula of the cyanate ion is shown below. What are the formal charges on the atoms in this ion? The options list the formal charges on O, C and N in that order. A. O: 0, C: 0, N: −1 B. O: −1, C: +1, N: −1 C. O: 0, C: −1, N: 0 D. O: −1, C: 0, N: 0
The structure of propynoic acid is shown below. Which row gives the hybridization of the atoms labelled X, Y and Z? A. X: sp, Y: sp3, Z: sp2 B. X: sp, Y: sp2, Z: sp2 C. X: sp2, Y: sp2, Z: sp3 D. X: sp2, Y: sp, Z: sp
What is the enthalpy change for the following reaction? CO2(g) + 4 H2(g) → CH4(g) + 2 H2O(l) A. +75 + 572 − 394 B. −75 − 572 − 394 C. +75 − 572 + 394 D. −75 − 572 + 394
Which allotrope of oxygen, O2 or O3, has the longer bond between oxygen atoms, and which is dissociated by ultraviolet radiation of the longer wavelength? A. Longer bond: ozone; longer wavelength: ozone B. Longer bond: oxygen; longer wavelength:…
Which combination of the signs of ΔH⊖ and ΔS⊖ describes a reaction that is spontaneous only at low temperature? The options list the sign of ΔH⊖ first. A. positive, positive B. positive, negative C. negative,…
The temperature of a sample of gas is raised from 27 °C to 177 °C. By what factor does the average kinetic energy of the gas particles change? A. 1.2 B. 1.5 C. 2.25 D. 6.6
The graph shows how the concentration of reactant A changes during a reaction. The dashed line is the tangent to the curve at t = 0. Which calculation gives the initial rate of reaction, in mol dm−3 s−1? A. B.…
The reaction between nitrogen dioxide and carbon monoxide, NO2 + CO → NO + CO2, is proposed to take place by the following mechanism. Step 1 (slow): 2 NO2 → NO3 + NO Step 2 (fast): NO3 + CO → NO2 + CO2 What is the order of reaction with…
Each option shows a graph of the concentration of a reactant against time and a graph of the rate against the concentration of that reactant. In which option do the two graphs correspond to the same order of reaction? A. Pair A B. Pair B C. Pair C D. Pair D
At a certain temperature the equilibrium constant for the reaction H2(g) + I2(g) ⇌ 2 HI(g) is Kc = 64. Which value is the equilibrium constant of the reaction below at that temperature? A. 32 B. 8.0 C. 0.125 D.…
Four reactions at 298 K have the equilibrium constants listed below. Which constant belongs to the reaction with the lowest (most negative) standard Gibbs energy change, ΔG⊖? A. 2.7 × 103 B. 3.1 × 10−4 C. 9.5 × 10−2…
Which products are formed when dilute hydrochloric acid reacts with solid calcium carbonate? A. Calcium chloride and water B. Calcium chloride, carbon dioxide and water C. Calcium chloride and hydrogen D. Calcium hydroxide and carbon dioxide
Which row correctly describes a weak Brønsted–Lowry acid? A. Ionizes only partially; its conjugate base is relatively strong B. Ionizes almost completely; its conjugate base is relatively strong C. Ionizes almost completely; its conjugate base is very weak D.…
The pKa of the ammonium ion, NH4+, is 9.25 at 298 K. What is the pKb of its conjugate base, NH3, at this temperature? A. −4.75 B. 4.75 C. 9.25 D. 23.25
A 20.0 cm3 sample of a weak monoprotic acid was titrated with a strong base. The graph shows the pH of the mixture as the base was added. What is the pH at the equivalence point? A. 4.7 B. 7.0 C. 8.7 D. 12.5
Which change involves the oxidation of chlorine? A. Cl2 → Cl− B. ClO4− → ClO3− C. Cl2 → ClO3− D. HCl → Cl−
Which row describes an electrolytic cell? A. The anode is positive; the overall reaction is non-spontaneous B. The anode is negative; the overall reaction is spontaneous C. The anode is negative; the overall reaction is non-spontaneous D. The anode is…
The standard electrode potentials of two half-cells are given below. The cell is represented as Which expression gives the standard cell potential, in V? A. 0.34 + 3(1.66) B. 0.34 + 1.66 C.…
A voltaic cell is assembled from the two half-cells below, connected by a salt bridge. Which statement is correct? A. Anions move from the salt bridge into the magnesium half-cell B. Anions move from the salt bridge into the copper half-cell C. Electrons flow…
Which formula represents an ester? A. CH3CH2OCH2CH3 B. CH3COOCH2CH3 C. CH3CH2CONH2 D. CH3CH2COOH
Benzene reacts with bromine in the presence of iron(III) bromide to form bromobenzene, not an addition product. Which statement best explains this? A. Benzene contains no carbon–carbon double bonds B. The carbon–carbon bonds in benzene are weaker than those in…
What is the product of the reaction between propene and bromine? A. 1,1-dibromopropane B. 2,2-dibromopropane C. 1,2-dibromopropane D. 1,3-dibromopropane
Which compound is optically active? A. propan-2-ol B. butan-1-ol C. 2-methylpropan-2-ol D. butan-2-ol
Which of the following pairs of reactants could form the carbocation intermediate shown? I. (CH3)2C=CHCH3 and HBr II. CH3CH2CH(CH3)CH2Br and H2O III. CH3CH2C(CH3)2Br and H2O A. I and II only B. I and III only C. II and…
Boron trifluoride reacts with ammonia to form an adduct. BF3 + NH3 → H3N−BF3 Which terms describe boron trifluoride in this reaction? A. Electrophile and Lewis base B. Nucleophile and Lewis acid C. Nucleophile and Lewis base D. Electrophile and Lewis…
A student determined the enthalpy of combustion of a fuel as −680 kJ mol−1. The literature value is −850 kJ mol−1. What is the percentage error of the experimental result? A. 20 % B. 25 % C. 80 % D. 125 %
Which compound produces the 1H NMR spectrum shown? The areas under the two signals are in the ratio 1 : 1. A. CH3COCH3 B. CH3COOCH3 C. CH3COOCH2CH3 D. CH3OCH3