Until well in the 60ties, the luminous dials of wrist watches and alarm clocks were marked with luminous paints containing Radium (Ra-226) or Promethium (Pm-147). These kind of watches are no longer manufactured today. This is not due to the radiation exposure to the persons wearing the watches but because of the radiological risk for the persons manufacturing them.
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Start by looking to the product there that doesn't have coefficient. Need to have exactly 2 Fe on the reactant side. So first coefficient is 2.. having a 2 there gives 2*3 = 6 H on the reactant side. Then in order to have 6 H on the product side the coefficient there needs to be 3. This gives 3 Ca on product side so there must be 3 Ca on reactant side.
coefficients:
2 + 3 --> 1 + 3
We first determine the complete reaction of the substances given above to tell whether precipitates are formed.
NaCl + NaBr = no reaction
NaCl + Na2CO3 = no reaction
<span>NaCl + BaCl2 = no reaction</span>
<span>NaCl + HCl = no reaction
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From all the substances given, reaction cannot happen therefore no precipitates are formed.
Substances are chemically combined and cannot be separated by normal physical means. Mixtures, however, are simply physically combined and can be separated into their component parts.