Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Unit
Principles of Chemistry
991 practice questions
Topics covered
- States of Matter102 practice questions
- Elements, Compounds and Mixtures69 practice questions
- Atomic Structure108 practice questions
- The Periodic Table103 practice questions
- Chemical Formulae, Equations and Calculations Part 119 practice questions
- Chemical Formulae, Equations and Calculations Part 2144 practice questions
- Ionic Bonding143 practice questions
- Covalent Bonding68 practice questions
- Metallic Bonding19 practice questions
- Electrolysis198 practice questions
Practice questions
271–280 of 991
Question 271
5 marks · Easy
Answer and see the solution →A sample of an element X consists of two isotopes. 30% of the atoms are isotope X-24 (with mass number 24) and 70% are isotope X-25 (with mass number 25). The atomic number of element X is 12.
(a)[3 marks]Calculate the relative atomic mass of element X from its isotopic abundances.
(b)[2 marks]How many electrons are there in an atom of X? State your answer and explain your reasoning.
Question 272
5 marks · Easy
Answer and see the solution →Two atoms of lithium are shown below.
Isotopes of lithium Isotope Mass number Atomic number Number of neutrons 6 3 7 3 (a)[2 marks]Complete the table by calculating the number of neutrons in each isotope.
(b)[2 marks]Describe one way in which the isotopes of lithium are the same, and one way in which they are different.
(c)[1 mark]State the number of electrons in a neutral atom of .
Question 273
5 marks · Easy
Answer and see the solution →An element X has two naturally occurring isotopes: X-64 and X-66. In a sample of X, 75% of the atoms are X-64 and 25% are X-66. The atomic number of X is 30.
(a)[3 marks]Calculate the relative atomic mass of element X. Show all your working.
(b)[1 mark]How many electrons are present in one atom of X?
(c)[1 mark]State the number of electrons in an ion of X with a 2+ charge.
Question 274
5 marks · Easy
Answer and see the solution →Use your knowledge of isotopes and atomic structure to answer the following questions about phosphorus.
(a)[2 marks]Describe two ways in which two isotopes of phosphorus are the same.
(b)[1 mark]Describe one way in which two isotopes of phosphorus are different.
(c)[1 mark]The atomic number of phosphorus is 15. State the number of electrons in a neutral atom of phosphorus.
(d)[1 mark]State the number of electrons in a phosphorus ion with a 3– charge.
Question 275
6 marks · Normal
Answer and see the solution →This question is about atoms, molecules, and the structure of the atom.
(a)State what is meant by each of the following terms:
(i)[1 mark]atom
(ii)[1 mark]molecule
(b)[3 marks]The diagram below represents a simple atom.
A simplified atom diagram showing a nucleus at (0,0) and two shells around it. Name the three types of sub-atomic particles found in atoms and state the position of each.
(c)[1 mark]The atomic number of lithium is 3, and its mass number is 7.
Calculate the number of each type of sub-atomic particle in one atom of lithium.
Question 276
6 marks · Normal
Answer and see the solution →A molecule of ammonia has the formula .
(a)[1 mark]State what is meant by the term molecule.
(b)[3 marks]Complete the table below for the sub-atomic particles in a nitrogen atom.
Properties of sub-atomic particles in a nitrogen atom Relative mass Relative charge Position in atom Proton Neutron Electron (c)Given that the atomic number of nitrogen is 7 and the mass number of its most common isotope is 14:
(i)[1 mark]Calculate the number of neutrons in a nitrogen atom.
(ii)[1 mark]Determine the total number of electrons in a molecule of ammonia ().
Question 277
6 marks · Normal
Answer and see the solution →Chlorine exists in nature as two main isotopes: and .
(a)[2 marks]Define the term isotope.
(b)[2 marks]Explain the difference between an atom and a molecule, using chlorine as an example.
(c)[2 marks]Given that the relative abundances of and are 75% and 25% respectively, calculate the relative atomic mass of chlorine. Show your working.
Question 278
6 marks · Normal
Answer and see the solution →A sample contains molecules of ammonia, .
(a)[2 marks]State the meanings of the terms 'atom' and 'molecule'.
(b)[2 marks]Each ammonia molecule contains one nitrogen atom (N) and three hydrogen atoms (H). The nitrogen atom in this molecule has a mass number of 15 and an atomic number of 7. Each hydrogen atom has a mass number of 1 and an atomic number of 1.
i. Calculate the total number of protons in one molecule of ammonia, using your answer to part (a) and the information above.
(c)[2 marks]ii. Calculate the total number of neutrons in one ammonia molecule, using the mass numbers given above.
Question 279
9 marks · Hard
Answer and see the solution →The Periodic Table symbol for the element bromine (B r) is shown below.
Symbol Mass number Name Atomic number Br 80 Bromine 35 Bromine has two main isotopes: B r-79 and B r-81.
(a)[2 marks]State the meaning of atomic number and mass number.
(b)For a neutral atom of bromine-80, calculate the number of:
(i)[1 mark]protons
(ii)[2 marks]neutrons
(iii)[1 mark]electrons
(c)[3 marks]Describe the relative mass and charge of each sub-atomic particle found in a bromine atom.
Question 280
1 mark · Easy
Answer and see the solution →State what the atomic number of an element represents.