Exam questions and answers

• At room temperature, the state symbol of oxygen is O2(g)
• In calcium carbonate, the percentage by mass of calcium is calculated by finding the mass of calcium and dividing it by the total mass of calcium carbonate
• The mean mass of solid after heating three samples of sodium nitrate is calculated by adding the masses and dividing by 3
• In the electronic structure of hydrogen and oxygen, hydrogen has 1 electron and oxygen has 2,6 electrons
• In an oxygen molecule, there are covalent bonds between the atoms of oxygen
• The boiling point of sulfur is higher than the boiling point of oxygen because in sulfur the intermolecular forces are stronger than in oxygen
• In the reaction of sodium with chlorine to produce sodium chloride, the balanced equation is 2Na + Cl2 ⟶ 2NaCl
• The mass of chlorine that reacted with 4.6 g of sodium to produce 11.7 g of sodium chloride is calculated by subtracting the mass of sodium from the mass of sodium chloride
• In the reaction of sodium with chlorine, sodium is a silver solid, chlorine is a green gas, the hot sodium burns with a lilac flame, and sodium chloride is a white solid
• The formulae of the ions in sodium chloride are Na+ and Cl-
• Potassium is more reactive than sodium because potassium loses an electron more easily than sodium
• The size of a potassium atom is larger than the size of a sodium atom because potassium has more electron shells
• Scientists used the atomic weight of an element to arrange elements in early periodic tables
• Mendeleev overcame problems in early periodic tables by leaving gaps for elements that had not been discovered
• The group that contains argon is the Noble gases
• An atom of argon has 18 protons and 22 neutrons
• The different atoms of argon are isotopes
• The electronic structure of an argon atom is 2, 8, 8
• Argon is unreactive because its outer electron shell is full
• The halogens are known as Group 7 in the periodic table
• A fluorine atom has 7 electrons in the outer shell
• Chlorine reacts with potassium bromide solution to produce potassium chloride and bromine
• Chlorine is more reactive than bromine because chlorine gains an electron more easily
• A chlorine atom is smaller than a bromine atom because chlorine has fewer electron shells
• Fluorine is a gas at room temperature because the forces between its molecules are weak due to its small size
• Copper chloride can conduct electricity when in solution or when molten
• In the electrolysis of copper chloride solution, Cl- and OH- ions move to the positive electrode because they are attracted to the positive charge
• H+ and OH- ions in the electrolysis of copper chloride solution come from water
• Cu2+ ion produces a metal in the electrolysis of copper chloride solution
• The mass of copper chloride in 40.0 cm3 of a copper chloride solution can be calculated using the given mass of copper chloride in 500 cm3
• Method for investigating temperature change when metal X is added to copper sulfate solution:

  1. Add 25 cm3 of copper sulfate solution to a beaker

  2. Measure the temperature of the copper sulfate solution

  3. Add 1.0 g of metal X and stir

  4. Measure the highest temperature reached when metal X is added to copper sulfate solution

  5. Repeat steps 1 to 4 with different metals
• In the investigation, the highest temperature reached when metal X was added to copper sulfate solution was 35.5 °C
• Variables to keep the same in the investigation:

  1. Volume of copper sulfate solution

  2. Amount of metal X added
• Mean temperature change for metal Y can be calculated by finding the average of the temperature changes in Test 1, Test 2, and Test 4
• The more reactive the metal added to copper sulfate solution, the greater the temperature change
• The student concludes metal A is zinc because the temperature change for metal A was 8 °C, which aligns with the reactivity series showing zinc as less reactive than magnesium
• When silver is added to copper sulfate solution, the temperature of the mixture increases
• One reason the student should not add potassium metal to copper sulfate solution is due to the high reactivity of potassium, which could lead to a violent reaction
• Mass of copper sulfate in 25 cm3 of the solution can be calculated using the given information about the concentration of copper sulfate in the solution
• Balanced equation for the reaction between magnesium and oxygen: 2Mg + O2 → 2MgO