Glucose, C₆H₁₂O₆, glyceraldehyde, C₃H₆O₃ and ethanoic acid, C₂H₄O₂ all have the empirical formula CH₂O. Glycerol, C₃H₈O₃ has the empirical formula C₃H₈O₃.

M_r CuSO₄.5H₂O = (64 + 32 + 64) + (5 x 18) = 250 so 125 g is 0.5 mol and contains 0.5 x 10 mol of H atoms = 3 x 10²⁴ H atoms.
6 g of H₂ contains 6 mol of H atoms = 3.6 x 10²⁴ H atoms; 23 g of ethanol (M_r = 46) is 0.5 mol so contains 0.5 x 6 mol of H atoms = 1.8 x 10²⁴ H atoms.  There are many moles of water in 5 dm³ of the HCl(aq) solution so the acid solution contains many more than 3 x 10²⁴ H atoms.

The balanced equation is (NH₄)₂Cr₂O₇ (s) →  Cr₂O₃ (s) + N₂ (g) + 4H₂O (g)

Amount of Zn = 6.5/65 = 0.1 mol. Zn(s) + H₂SO₄(aq)  → ZnSO₄(aq) + H₂(g) so amount of hydrogen produced = 0.1 mol. 1.0 mol of gas produced at STP (273 K,  1 x 10⁵ Pa ) occupies 22.7 dm³,  so volume of H₂ produced at 310 K = 0.1 x 22.7 x 310/273 dm³.

The visible series is produced by electrons transitioning from higher levels to the n = 2 level. The first line in the visible series is due to n = 3 to n = 2, the second line n = 4 to n = 2 and the third line from n = 5 to n = 2.

The atomic number, Z is 31 so it contains 31 protons. The mass number, A is 71 so it contains 40 neutrons. It is the 3+ ion so it contains 31 minus 3 electrons.

The atomic radius increases upon descending both groups. The first ionization energy and electronegativity both decrease upon descending both groups. Melting points decreases from Li to Cs but increase from F to I.

First ionization energies generally increase across a period but decrease between ns² and ns²np¹ and between ns²np³ and ns²np⁴

The lead(II) ion is Pb²⁺ and the sulfate ion is SO₄²⁻.

The greater the difference in the electronegativity values of the two atoms making up a covalent bond the greater the polarity. Fluorine has the highest negativity value (4.0). Hydrogen and carbon have similar values (2.2 and 2.6 respectively) and chlorine (3.2) and oxygen (3.4) are both less than fluorine.

There are only six electrons (three bonding pairs) around the boron atom in BCl₃. AlCl₃ also has an incomplete octet but when it dimerises to form Al₂Cl₆ coordinate bonds are formed between Cl and Al to complete the octet. The carbon atom in CHCl₃ has four bonding pairs of electrons and the phosphorus atom in PCl₃ contains three bonding and one non-bonding pairs of electrons.

Graphene consists of a layer of interlocking hexagonal rings with bond angles of 120^o.  Water and ammonia contain 4 electron domains around the central atom so have bond angles less than 109.5^o due to repulsion between the non-bonding pair(s) of electrons and the bonding pairs. Carbon dioxide is linear as the two electron domains are made up of two double bonds each between the C and O atoms.

In an endothermic reaction the product has a greater enthalpy than the reactants and the sign of ΔH is positive.

50.0 cm³ of 1.00 mol dm⁻³ hydrochloric acid, HCl(aq) contains 50.0/1000 = 0.05 mol so amount of heat evolved = 57.6 x 0.05 = 2.88 kJ. Total volume of solution = 100 cm³, so mass of solution = 0.100 kg.
ΔT = 2.88 ÷ (4.18 x 0.1) = 28.8 ÷ 4.18 ^oC 

Average bond enthalpies only refer to the gaseous state. To form gaseous prop-2-ene the bonds broken are C=C and H−Br so the energy in = 614 + 366 kJ. The bonds formed are C−Br, C−C and C−H so the energy out = − (285 + 346 + 414) kJ. The change in enthalpy = − [(285 + 346 + 414) − (614 + 366)] kJ. However the product is in the liquid state so a further 30 kJ of energy will be given out as the gas condenses to a liquid so ΔH = − [(285 + 346 + 414) − (614 + 366) + 30] kJ.

Although increasing the concentration of the reactants, increasing the pressure of gaseous reactants, increasing the temperature and decreasing the particle size (i.e. increasing the surface area) of solid reactants all increase the rate of the reaction they do this by either increasing the number of collisions or by increasing the energy of the particles so that more possess the minimum energy required to react. The addition of a suitable catalyst changes the reaction pathway to one with a lower activation energy.

The temperature of the solution, volume of gas  evolved and mass of remaining reactants as the carbon dioxide evolves all change over time. There is no change in colour over time as the white calcium carbonate solid dissolves in colourless hydrochloric acid to give a colourless solution.

K_c is a constant at a specified temperature so altering the pressure has no effect on the value of K_c. The reaction is exothermic as ΔH has a negative value so lowering the temperature will shift the position of equilibrium towards the products and increase the value of the equilibrium constant.

The conjugate base is formed when a proton is donated, OH⁻(aq) → H⁺(aq) + O²⁻(aq)

Hydrogencarbonates are basic and are neutralised by acids forming a salt, carbon dioxide and water, HCl(aq) + NaHCO₃ → NaCl(aq) + CO₂(g) + H₂O(l).

Strong acids are completely dissociated into ions so have a higher electrical conductivity than weak acids which are only partially dissociated. [H+(aq)] will be higher for strong acids so the pH will be lower.

H has an oxidation state of +1 (except for hydride, H⁻, ions where it is −1 ) and O has an oxidation state of −2 (except for peroxides −O−O− where it is −1) so iodine must have an oxidation state of +5 in iodic acid to give the sum of the oxidation states equal to zero. In hypoiodous acid the oxidation state of iodine is +1, in iodine dioxide it is +4 and in orthoperiodic acid it is +7.

When hydrogen peroxide decomposes it simultaneously oxidises and reduces itself so that the oxidation state of oxygen in hydrogen peroxide (+1) increases to zero in oxygen and decreases to minus two in water (this is an example of disproportionation). When it acts as a reducing agent, as with KMnO₄ and NaOCl, oxygen is formed and when it acts as an oxidising agent, as with FeSO₄, it is reduced to water.

Oxidation in both cells always occurs at the anode but in an electrolytic cell it is the positive electrode whereas in a voltaic cell it is the negative electrode. Voltaic cells generate electricity from a spontaneous chemical process whereas in electrolytic cells electricity is used to bring about a non-spontaneous chemical process.

A tertiary carbon atoms is bonded to a functional group such as a halogen or -OH and to three R groups (the R groups may be the same as each other or different). A tertiary carbon atom is not bonded to a hydrogen atom.

>C=O, >C=C< and −OH (carbonyl, alkenyl and hydroxyl) are all present. −CHO, C₆H₅− and R−O−R' (aldehyde, phenyl and ether) are all absent.

In the presence of a sulfuric acid catalyst, carboxylic acids condense with alcohols to form an ester and water.
CH₃CH₂COOH + CH₃CH(OH)CH₃ → CH₃CH₂COOCH(CH₃)₂ + H₂O

The number of significant figures in a result is based on the figures given in the data. Since the concentration of the potassium hydroxide solution is only given to two significant figures the concentration of the hydrochloric acid solution should only be quoted to two significant figures.

When determining IHD, O atoms count as zero. For each N atom add one to the number of C atoms and add one to the number of H atoms. This gives the equivalent of C₇H₈ which needs 8 more hydrogen atoms (4 units of H₂) to become saturated as C₇H₁₆, hence the IHD is 4. 

Bond vibrations (stretching and bending) occur in the infrared region. Since different bonds vibrate at different frequencies infrared spectroscopy can be used to identify different functional groups.