Chapter 3 SABIS Grade 10 Part 6 Practice
📝 Lesson 15 📝
Question 57: Qualitative properties of gases studied: Reaction with air Among the gases NO2, Cl2, O2, H2, NO, NH3, HCl, identify the gas that reacts with cold air, the gas that explodes when a lit splint is introduced to it in air, and the gas that makes a glowing splint catch fire.
Answer 57: Reacts with cold air: NO (nitrogen monoxide) Explodes when a lit splint is introduced to it in air: H2 (hydrogen) Makes a glowing splint catch fire: O2 (oxygen)
Question 58: Qualitative properties of gases: Effect on litmus paper Among the gases NO2, Cl2, O2, H2, NO, NH3, HCl, determine the gas that turns wet red litmus blue, the gas that turns wet blue litmus red, and the gas that "bleaches" litmus paper.
Answer 58: Turns wet blue litmus paper blue: NH3 (ammonia) Turns wet blue litmus paper red: NO2 (nitrogen dioxide) "Bleaches" wet litmus paper: Cl2 (chlorine)
Question 59: Qualitative properties of gases: Solubility in water Out of the gases NO2, Cl2, O2, H2, NO, NH3, HCl, identify the gases that are very soluble in water.
Answer 59: The gases that are very soluble in water are:
NO2 (nitrogen dioxide)
NH3 (ammonia)
HCl (hydrogen chloride)
Question 60: Qualitative properties of gases: Color Among the gases NO2, Cl2, O2, H2, NO, NH3, HCl, there are two gases that exhibit color. Identify these gases and specify their respective colors.
Answer 60: The two gases that exhibit color are:
NO2 (nitrogen dioxide) - Color: Reddish brown
Cl2 (chlorine) - Color: Yellowish green
🔍 Question 61: Ratio in which gases react Gay-Lussac generalized that when gases react: a) they do so in fixed ratios that could not be simplified into small number ratios. b) some react in the ratio of small whole numbers, while others reacted in fixed ratios that could not be simplified into small number ratios. c) they always do so in ratios of small whole numbers.
📝 Answer 61: Gay-Lussac's generalization states that when gases react: a) Some gases react in fixed ratios that cannot be simplified into small number ratios. b) Other gases react in the ratio of small whole numbers. c) In general, gases always react in ratios of small whole numbers.
🔍 Question 62: Avogadro’s hypothesis Avogadro’s hypothesis states that: a) gases always react in whole-number ratios. b) equal volumes of different gases have equal masses, at the same temperature and pressure. c) equal volumes of different gases have equal numbers of particles, at the same temperature and pressure.
📝 Answer 62: Avogadro’s hypothesis states: a) Gases always react in whole-number ratios. b) Equal volumes of different gases have equal masses at the same temperature and pressure. c) Equal volumes of different gases have an equal number of particles at the same temperature and pressure.
🔍 Question 63: Given volumes reaction ratio, find ratio by molecules At 200°C, one volume of oxygen gas combines with two volumes of hydrogen gas to form two volumes of steam. From these data and Avogadro's Hypothesis, how many molecules of hydrogen combine with one molecule of oxygen, and how many molecules of steam are produced?
📝 Answer 63: According to Avogadro's Hypothesis, at 200°C:
One molecule of oxygen combines with two molecules of hydrogen to form two molecules of steam.
🔍 Question 64: Dalton's atomic theory a) What is the statement of Dalton’s atomic theory?
The simplest substances found in nature are called elements.
Atoms of one element are all identical.
Elements combine to form compounds.
One atom of one element combines with one atom of another element to form one molecule of a compound.
The smallest particle of a compound is a molecule.
Atoms cannot be created nor destroyed; atoms are always conserved.
b) What are the simplest substances in nature called? Elements c) What do we call the particles formed when different atoms combine? Molecules d) What do elements form when they combine? Compounds e) How can atoms be created? How can atoms be destroyed? Atoms cannot be created nor destroyed.
📝 Answer 64: a) Dalton's atomic theory states:
The simplest substances found in nature are called elements.
Atoms of one element are all identical.
Elements combine to form compounds.
One atom of one element combines with one atom of another element to form one molecule of a compound.
The smallest particle of a compound is a molecule.
Atoms cannot be created nor destroyed; atoms are always conserved.
b) The simplest substances in nature are called elements. c) When different atoms combine, they form molecules. d) Elements form compounds when they combine. e) Atoms cannot be created nor destroyed; they are conserved.
🔍 Question 65: Assumptions needed for Avogadro’s hypothesis to apply If Avogadro’s hypothesis is correct, which of the following assumptions is necessary? a) At least some gaseous elements are diatomic. b) Atoms may react in whole number ratios other than one to one. c) Atoms can react in ratios that cannot be simplified to whole number ratios.
📝 Answer 65: For Avogadro’s hypothesis to apply, the necessary assumption is: a) At least some gaseous elements are diatomic.
🔍 Question 66: Know the meaning of atomicity What is meant by the atomicity of a molecule?
📝 Answer 66: The atomicity of a molecule refers to the number of atoms present in the molecule.
🔍 Question 67: Know the meaning of “operational definition” An operational definition defines a term through: a) actions you can perform in the laboratory. b) arithmetical operations and symbols. c) theoretical concepts.
📝 Answer 67: An operational definition defines a term through actions you can perform in the laboratory.
🔍 Question 68: Know the meaning of “conceptual definition” A conceptual definition defines a term through: a) actions you can perform in the laboratory. b) arithmetical operations and symbols. c) theoretical concepts.
📝 Answer 68: A conceptual definition defines a term through theoretical concepts.
🔍 Question 69: Know the operational definition of a pure substance How do you recognize a pure substance?
📝 Answer 69: A pure substance is recognized by determining its physical properties. We measure physical constants such as melting point. The physical properties of a pure substance must be fixed and constant.
🔍 Question 70: Know the conceptual definition of a pure substance (one type of particle) How do we explain the behavior of a pure substance, i.e. what conceptual explanation do we give?
📝 Answer 70: A pure substance is a substance that contains only one kind of particles (atoms or molecules). Its behavior can be explained by the presence of a single type of particle.
🔍 Question 71: Know how to identify a pure substance
How do you identify a given pure substance? (e.g. to know whether it is water or alcohol).
To identify the pure substance, we look at the physical constants measured and compare them with listed values. For example, the boiling point of water is 100°C while the boiling point of ethanol is 78°C. Physical properties depend on the nature of the pure substance only. Pure substances can be either elements or compounds.
🔍 Question 72: Know that a pure substance can be either an element or a compound
Which of the following is a pure substance?
a) Gold (jewelry gold is not a pure substance) b) Milk c) Water d) Seawater e) Sand.
📝 Answer 72: The pure substance among the options is: a) Gold (jewelry gold is not a pure substance)
🔍 Question 73: The conceptual definition of a compound
What is the conceptual definition of a compound?
A compound is a pure substance that has one type of molecules, containing more than one type of atoms.
🔍 Question 74: The operational definition of a compound
What is the operational definition of a compound?
A compound is a pure substance that can be split into simpler substances by chemical means.
🔍 Question 75: Recognize a compound which is not made up of molecules
What is an example of a compound not made up of molecules?
a) Sodium b) Water c) Table salt (NaCl, sodium chloride) d) HCl e) Oxygen.
📝 Answer 75: The compound not made up of molecules among the options is: a) Sodium
🔍 Question 76: The operational definition of an element
What is the operational definition of an element?
An element is a pure substance that cannot be split into simpler substances by physical or chemical means.
🔍 Question 77: The conceptual definition of an element
What is the conceptual definition of an element?
An element is a pure substance that has one type of atoms.
🔍 Question 78: Give an example of a heterogeneous substance
Which of the following is a heterogeneous substance?
a) Cola drink (if freshly open) b) Cola drink (after a while) c) Air d) Table sugar e) Whole-grain bread f) Sand
🔍 Question 79: Give an example of a homogeneous substance
Which of the following is NOT a homogeneous substance?
a) Sand b) Talcum powder c) Salt solution d) White flour
🔍 Question 80: Categorize substances as mixtures or pure substances
Classify each of the following as a pure substance or a mixture:
a) Cola drink. Mixture b) Air. Mixture c) Solid carbon dioxide. Pure substance d) Bread. Mixture e) Flour. Mixture f) Hydrogen gas. Pure substance g) Sea water. Mixture h) Orange juice. Mixture i) Zinc metal. Pure substance
🔍 Question 81: Categorize substances as elements or compounds
Classify each of the following pure substances as element or compound:
a) Nitrogen dioxide gas. Compound b) Helium gas. Element c) Liquid bromine. Element d) Pure gold. Element e) Water. Compound f) Table salt (NaCl). Compound g) Table sugar (C6H12O6). Compound
🔍 Question 82: Recognize the symbols H, O, N, C, Cl, Na, Mg, Ca, Si, P, S
What is the symbol for:
a) Sodium. Na b) Carbon. C c) Magnesium. Mg d) Phosphorus. P e) Chlorine. Cl f) Scandium. Sc g) Sulfur. S
🔍 Question 83: Know what chemical formula means
Which of the following is true of a chemical formula?
a) In the case of molecular compounds, it is also known as the molecular formula. b) It gives the number and the kind of atoms of each element in a molecule of that compound. c) It can be used to obtain the simplest ratio of atoms in the molecular compound. 🔍 Question 84: Recognize molecular formulas
Which of the following compounds has a molecular formula? In these cases, what is it? In case there is no molecular formula, why not?
a) Gaseous ethane (dicarbon hexahydride C2H6) has a molecular formula: C2H6 b) KCl: Ionic compound, it has no molecular formula as it is made up of ions, not molecules c) Na solid: It is an atom
🔍 Question 85: Know what simplest formula means
Which of the following is true of a simplest formula?
a) In the case of compounds, it is also known as the molecular formula. b) In the case of molecular compounds, it gives the simplest ratio in which the atoms are found together. c) In the case of salt, it gives the simplest ratio in which the ions are found together.
🔍 Question 86: Find the simplest formula from the chemical formula
Which of the following gives the WRONG simplest formula?
a) Sodium Chloride: NaCl b) Glucose (C6H12O6): CH2O c) Dinitrogen tetroxide N2O4 (the correct simplest formula is NO2) d) Nitrogen dioxide: NO2 e) Benzene, C6H6: CH
🔍 Question 87: Know the meaning of empirical formula
The simplest formula of ethane is CH3. Find its empirical formula.
Which of the following is true about the empirical formula?
a) It is the same as the molecular formula. b) It is the same as the simplest formula. c) It shows the structure of the atoms in the molecule. 🔍 Question 88: Representation of a chemical bond
On paper, how do we represent a chemical bond? 📝
Scientists represent the chemical bond holding the two atoms with a solid line joining the symbols of the two atoms, "—"
🔍 Question 89: What a structural formula shows
What does the structural formula of a compound show? Explain by showing the difference between the chemical and structural formulas of water. 📝
The structural formula shows everything that the molecular formula shows (kind of atoms making up the molecule, atomicity, number of atoms of each type of atom in the molecule) and more. A structural formula shows how atoms are bonded to each other in the molecule.
🔍 Question 90: Recognizing a structural formula
Which of the formulas below is a structural formula? 📝
a) C2H6 b) (CH)3 c) 2O2 d) H⎯Be⎯H e) H⎯N⎯H
🔍 Question 91: What molecular models are
What are molecular models? They are: 📝
a) Tiny representations of molecules. b) Balls representing atoms, joined together by sticks or springs. c) Structures drawn on paper to show how atoms in a molecule are connected together.
🔍 Question 92: What molecular models show that structural formulas do not
Why do we use three-dimensional models instead of only using structural formulas? 📝
a) So we can visualize shapes in three dimensions. b) To show on a large scale what molecules really look like. c) So that teachers have something to show to students.
🔍 Question 93: Particles of matter in liquids and solids
Which of the following hypotheses is accepted by scientists? 📝
a) When a gas becomes a liquid or solid, all particles melt together into one larger particle or object. b) In a liquid or solid, particles are very close together, so an object cannot be compressed any further, whereas in the gaseous state particles have a lot of empty space between them. c) In a liquid or a gas, particles are free to move with respect to each other, but in a solid, particles are locked in specific positions.
🔍 Question 94: What a mole is
a) What is a mole? 🧪
A mole is Avogadro's number of particles (6.02x10²³). A mole is the number of atoms found in 12.000 g of Carbon-12.
b) What is Avogadro's number? 6.02x10²³ c) What is the number of molecules in 22.4 dm³ of an ideal gas at 0°C and 1 atmosphere pressure? 6.02x10²³
🔍 Question 95: Defining the amu
The amu is defined as: 📏
a) 1/12 of the mass of an atom of C-12 (an isotope of carbon). b) The mass of an atom of C-12 (an isotope of carbon). c) The mass of one gram of C-12 (an isotope of carbon). d) The mass of one gram of any material. e) The mass of 22.4 dm³ of C-12 at 0°C and 1 atm.
🔍 Question 96: The relation between a gram and the amu
Give the relation between a gram and an amu. 📏
1g = 6.02x10²³ amu
🔍 Question 97: Find the mass of one atom in grams
Find the mass of 1 atom of oxygen in grams. 🧪
Mass of 1 atom of oxygen = 16 amu 1 g = 6.02x10²³ amu Mass of 1 atom of oxygen in grams = (1 g / 6.02x10²³ amu) * 16 amu
🔍 Question 98: Meaning of the atomic mass of an element
The atomic mass of iron, Fe, is 56. We can conclude that: 📚
a) 1 atom of Fe has a mass of 56 amu. b) 1 mole of Fe has a mass of 56 amu. c) 6.02x10²³ atoms of Fe have a mass of 56 g. d) Mass of Fe atom relative to C-12 atom is 56 to 12.
🔍 Question 99: Table of atomic masses gives RELATIVE masses of atoms
The table of atomic masses gives the relative masses of atoms. Relative to what? 📚
Relative to the mass of a carbon-12 atom.
🔍 Question 100: Find the molecular mass of a compound
Find the molecular mass of the following compound. 🧪
a) H2SO4: 2(1) + 32 + 4(16) = 98 b) C2H6: 2(12) + 6(1) = 30 c) CO2: 12 + 2(16) = 44