AS PPQs Paper 1

Explain why the first ionisation energy of sulfur is different from that of phosphorus. (2)

-e⁻ paired in 3p orbital in S -Paired e⁻ repel so less energy needed to remove

Explain how ions are accelerated, detected and have their abundance determined in a time of flight (TOF) mass spectrometer.

-ions accelerated by attraction to negatively charged plate -ions detected by gaining electrons -abundance determined by size of current flowing (or amount of electrons gained) in the detector

Give the full electron configuration of an Al atom and of a Cr³⁺ ion. (2)

Al atom→ 1s²2s²2p⁶3s²3p¹ Cr³⁺→ 1s²2s²2p⁶3s²3p⁶3d³

mol MHCO₃= ANS x 3.1 x 10= 9.89x10⁻³ Mr=1464÷1000/9.89x10⁻³ Mr= 148 (3sf)

Calculate the amount, in moles, of MHCO₃ IN 250cm³ of the solution. Then calculate the experimental value for the Mr of MHCO₃. Give your answer to the appropriate number of significant figures. (3)

Deduce the formula of the compound that contains 2+ions and 3- ions that both have he same electron configuration as argon. (1)

Ca₃P₂

Calculate the mass, in kg, of a single ⁵²Cr⁺ ion. Assume that the mass of a ⁵²Cr⁺ ion is the same as that of a ⁵²Cr atom. (Avoradro constant= 6.022 x 10²³mol⁻¹)

Mass= 52÷1000/6.022x10²³ Mass= 8.64x 10⁻²⁶

Write an equation to represent the process that occurs when the first ionisation energy for sodium is measured. (1)

Na(g) → Na⁺(g) + e⁻

This question is about Period 3 of the Periodic Table. Deduce which of Na⁺ and Mg²⁺ is the smaller ion. Explain your answer. (2)

Smaller ion→ Mg Explanation→ Because Mg²⁺ has more protons and with the same shielding

Deduce the formula of the ion that has a charge of 2+ with the same electron configuration as krypton. (1)

Sr²⁺

Another student is required to make up 250cm³ of an aqueous solution that contains a known mass of MHCO₃. The student is provided with a sample bottle containing the MHCO₃. Describe the method, including apparatus and practical details, that the student should use to prepare the solution. (6)

Stage 1: transfers of known mass of solid a) Weigh the sample bottle containing the solid on a (2dp) balance b) Transfer to a beaker and reweigh sample bottle c) Record the difference in mass Stage 2: dissolves in water a) Add distilled/deionised water b) Stir c) Until all solid has dissolved Stage 3: transfer, washing and agitation a) Transfer to volumetric/graduated flask. b) With washings c) Make up to 250cm³ d) Shake/invert

The student identified use of the burette as the largest source of uncertainty in the experiment. Using the same apparatus, suggest how the procedure could be improved to reduce the percentage uncertainty in using the burette. Justify your suggested improvement. (2)

Suggestion→ Use a larger mass of solid or use a more concentrated solution of MHCO₃ or less concentrated/more dilute of HCl Justification→ So a larger titre/reading will be needed or larger volume of HCl

Mean titre= 9.75 + 9.65/2= 9.7cm³ mol HCl= 0.102 x 9.7÷1000=9.89x10⁻⁴

This question is about a white solid, MHCO₃, that dissolves in water and reacts with the hydrochloric acid to give salt. MHCO₃ + HCl → MCl + H₂O + CO₂ A student was asked to design an experiment to determine a value for the Mr of MHCO₃. The student dissolved 1464mg of MHCO₃ in water and made the solution up to 250cm³. 25.0cm³ samples of the solution were titrated with 0.102 mol dm⁻³ hydrochloric acid. The results are shown in Table 1. Calculate the mean titre and use this to determine the amount, in moles, of HCl that reacted with 25.0cm³ of the MHCO₃ solution. (3)

In a TOF mass spectrometer the kinetic energy of a ⁵²Cr⁺ ion was 1.269x10⁻¹³J. Calculate the velocity of the ion using the equation.

V²=(2x1.269x10⁻¹³)/