Chemistry Crit A

• What does the FLAME TEST test for?


  Cations
• What does the SODIUM HYDROXIDE TEST test for?


  Cations
• Lithium (Li) burns a red flame
• Sodium (Na) burns a yellow-orange flame
• Potassium (K) burns a lilac flame
• Calcium (Ca) burns a orange-red flame
• Copper (Cu) burns blue-green flame
• Ammonium (NH4) when added to sodium hydroxide releases ammonia gas (pungent smell)
• Copper (Cu2+) when added to sodium hydroxide releases a blue precipitate of Cu(OH)2 - Copper Hydroxide
• Iron (Fe2+) when added to sodium hydroxide releases a green precipitate of Fe(OH)2 - iron hydroxide
• Ferric iron (Fe3+) when added to sodium hydroxide releases a brown precipitate of Fe(OH)3
• Sodium hydroxide is an alkali
• Chlorine (Cl-) in silver nitrate test = White precipitate of AgCl (Silver chloride)
• Bromine (Br-) in silver nitrate test -Creamy precipitate of AgBr (Silver bromide)
• Iodine (I-) in silver nitrate test = yellow precipitate of AgI (Silver Iodide)
• Carbonate (CO3 2-) in hydrochloric acid = CO2 produced
• Name the two subatomic particles that are found in the nucleus and state their charges.

  The nucleus is made up of protons and neutrons. Protons are positively charged and neutrons have no charge (they are neutral).
• What does atomic number represent?

  The atomic number (the smaller number) tells us the number of protons in the nucleus of that atom. Since the number of protons is equal to the number of electrons (in a neutral atom), then it also tells us the number of electrons around the nucleus.
• Why do atoms have an overall neutral charge?

  Protons have a positive charge while electrons have a negative charge. Atoms have the same number of electrons as they have protons so the positive charges exactly cancel out the negative charges, resulting in a neutral atom.
• Sodium (Na) has an atomic number of 11 and a mass number of 23. State the number of protons, neutrons and electrons in a sodium atom.

  11 protons, 12 neutrons, 11 electrons
• What is an isotope?

  Isotopes are atoms of an element with the same number of protons but different numbers of neutrons. An example would be carbon-12 and carbon-13, both of which have 6 protons in their nucleus but carbon-13 has an extra neutron compared to carbon-12.
• RAM formula

  (mass no. of isotope 1 x percentage of isotope 1) + (mass no. of isotope 2 x percentage of isotope 2) / 100