of moles of CO2 = 72/(24 000) = 0.003 mol no. of moles of C = no. of moles of CO2 (from the formula, CO2, and the = 0.003 mol equation, C + O2 CO2) mass of C = 0.003 x 12.0 = 0.036 g mass of Al = 0.144 – 0.036 = 0.108 aluminium carbon mass (g) 0.108 0.036 molar mass 27.0 12.0 (mass )/(molar mass) = no. of moles 0.108/27.0 = 0.004 0.036/12.0 = 0.003 ratio 4 3 Hence, the empirical formula of X is Al4C3. Example
Describe the differences between protons and electrons The difference between protons and electrons is that protons are positively charged and that elections are negatively charged. Another difference is that protons are in the nucleus and electrons circle the nucleus in shells outside the nucleus. What is the difference between the mass number and the relative atomic mass of an element? The difference between the mass number and the atomic mass is that the mass number is the number of protons and neutrons in the nucleus and the relative atomic mass is the mass of an atom. Distinguish between an element and a compound with 2 examples for each An element is a substance that cannot be broken down into any simpler substances.
Neutrons, Protons and electrons are all sub-atomic particles. In relative mass, we always think of protons and neutrons in having a mass of 1 and electrons a mass of 1/1840, which shows that electrons are considerably smaller than protons and neutrons, and only make up a small part of the atom. The amount of protons and neutrons added together is the relative atomic mass, and this is the main structure of the atom. 2. The arrangement of particles in an atom Protons and neutrons make up the main, dense, central nucleus in the centre of the atom.
* Avogadro’s constant: The number of toms per mole is called the Avogadro’s constant. It has a value of 6.02x10^23. * Relative atomic mass: The relative atomic mass of an element is the average mass of one atom of the element relative to 1/12th the mass of one atom of carbon-1 (Ar), On a scale
The atomic masses of two isotopes of cobalt are 59 and 60. a) What is the number of protons and neutrons in each? • The protons are the same otherwise it wouldn't be cobalt = 27 So the remainders are neutrons = 32 or 33 b) What is the number of orbiting electrons in each when the isotopes are electrically neutral? • Electrons = protons = 27, if electrically
INTRODUCTION TO NUCLEAR REACTION: The main features of nuclear reactions include radioactive decay, nuclear fission and nuclear fusion. Radioactive decay: Energy is released in a radioactive decay in the form of the kinetic energy of the particle emitted (α and β), the kinetic energy of the daughter nucleus and the energy of the gamma-ray photon that may accompany the decay. The energy involved may be calculated by finding the mass defect of the reaction. The energy released is the energy equivalent of the mass defect of the reaction. Nuclear fission: Nuclear fission is the process in which a large nucleus breaks into two smaller nuclei that are almost equal in mass.