Edexcel GCSE Combined Science Paper 3: Chemistry 1 Higher June 2024 question paper 1SC0/1CH

Barium hydroxide reacts with dilute hydrochloric acid to form barium chloride solution and water.

Complete the balanced equation for the reaction by adding a number in front of HC l (aq).

Ba(OH)₂(s) +_........ HCl(aq) BaCl₂(aq) + 2H₂O(l)

State what you would see during the reaction.

A student investigated how the pH of the mixture changed as barium hydroxide was added to dilute hydrochloric acid.

The student used this method.

step 1 measure out 50 cm3³ of dilute hydrochloric acid into a beaker using a measuring cylinder

step 2 use a glass rod to place a drop of the acid onto a piece of universal indicator paper and record the pH

step 3 add one spatula measure of barium hydroxide to the acid in the beaker and stir

step 4 use the glass rod to place a drop of the mixture onto a new piece of universal indicator paper and record the pH again

step 5 repeat steps 3 and 4 until there is no further change in the pH.

Name a piece of equipment that could be used to measure the pH of a substance more accurately than universal indicator paper.

Explain why, in step 3, the mixture was stirred after adding the barium hydroxide.

Figure 1 shows the student’s results.

Plot a graph of the pH of the mixture against the number of spatula measures of barium hydroxide.

Use the graph to find the pH of the mixture when 4.5 spatula measures of barium hydroxide are added.

pH of the mixture =_........

Sodium carbonate has the formula Na₂CO₃.

Sodium carbonate contains Na⁺ ions and CO₃^2– ions.

The atomic number of sodium is 11.

What is the electronic configuration of the Na⁺ ion?

Explain why solid sodium carbonate cannot conduct electricity but a solution of sodium carbonate can conduct electricity.

Calculate the percentage by mass of sodium in sodium carbonate, Na₂CO₃.

(relative atomic masses: C = 12, O = 16, Na = 23)

percentage by mass of sodium =_........

This question is about the extraction of metals.

Give two advantages of obtaining metals by recycling rather than by extracting them from their metal ores.

Small amounts of some metals are extracted using displacement reactions.

In one process, zinc dust is used to precipitate cadmium metal from a solution containing cadmium ions.

cadmium ions
cadmium

Explain why this displacement reaction can be described as a redox reaction.

The formula of the cadmium ion is Cd²⁺. The formula of the phosphate ion is PO₄^3–.

Which is the formula of cadmium phosphate?

One of the alternative biological methods of extracting metals from very low‑grade ores is bioleaching using bacteria.

Give one disadvantage of this method of extracting metals from low‑grade ores.

Lead is low in the reactivity series.

Describe how to obtain a sample of lead from some lead oxide in the laboratory.

Water, acidified with dilute sulfuric acid, was electrolysed for 10 minutes using inert electrodes.

Figure 2 shows the apparatus used.

In this electrolysis, the acidified water is an electrolyte.

Explain why acidified water is an electrolyte.

Hydrogen collects at the negative electrode and oxygen collects at the positive electrode.

Which of these shows the results after 10 minutes of this electrolysis?

Complete and balance the half equation for the formation of oxygen at the positive electrode in this electrolysis.

4OH^– _........

Copper sulfate solution was electrolysed for 10 minutes using copper electrodes.

Figure 3 shows the mass of the cathode and the appearance of the copper sulfate solution before electrolysis and after electrolysis.

Describe what should be done to the copper cathode, after it has been removed from the copper sulfate solution, before its final mass is determined.

Explain, in terms of ions, the change in mass of the cathode shown in Figure 3.

Explain why the appearance of the copper sulfate solution did not change during the electrolysis.

This question is about the properties of different substances.

Silicon tetrachloride is a simple molecular covalent compound.

A molecule of silicon tetrachloride is composed of a silicon atom and four chlorine atoms.

• a silicon atom has 4 outer electrons

• a chlorine atom has 7 outer electrons

Draw a dot and cross diagram of a molecule of silicon tetrachloride, SiCl₄.

Show outer electrons only.

Explain why simple molecular covalent compounds such as silicon tetrachloride have low melting and boiling points.

Part of the structure of rubidium bromide is shown in Figure 4.

Which row shows the most likely melting point and boiling point of rubidium bromide?

*(c) Diamond and graphite are two forms of carbon.

Figure 5 shows how the carbon atoms are arranged in a part of the structure of each of these forms of carbon.

• diamond is one of the hardest known substances on Earth and is used in cutting tools.

• graphite is soft and flaky.

• diamond is a poor electrical conductor, but graphite is a good electrical conductor.

Explain, in terms of structure and bonding, these properties of diamond and graphite.

An investigation was carried out on the reactivity of four metals, D, E, F and G.

Equal sized pieces of these metals were placed in excess dilute hydrochloric acid and left for three minutes.

Figure 6 shows the observations of the reactions for metals D, E and F.

The order of reactivity for these metals is shown in Figure 7.

most reactive
least reactive

Figure 7

Use the information in Figure 6 and Figure 7 to suggest the observations that would be made for metal G.

The dilute hydrochloric acid used in this reaction is a strong acid.

Explain the meaning of the terms dilute and strong acid.

dilute

strong acid

The formula of lead ethanoate is Pb(CH₃COO)₂.

Calculate the number of atoms that combine together to form 16.25 g of lead ethanoate.

(relative atomic masses: H = 1.00, C = 12.0, O = 16.0, Pb = 207

Avogadro number = 6.02×10²³)

number of atoms =_........