Hi, you've asked an incomplete question. However, I assumed you are referring to the article found on the Scientific American website.
Explanation:
<em>Remember,</em> according to that article we are told that scientists notice that these insects have a long nymphal (immature form before becoming adults) stage, one that can last up to 13 to 17 years on the ground before they leave the ground looking for mating partners.
Because it is only after mating occurs at this point that their eggs are laid, that is why scientists believe that cicadas only reproduce every 13 or 17 years.
Answer:
74.81 grams of calcium carbonate are produced from 79.3 g of sodium carbonate.
Explanation:
The balanced reaction is:
Na₂CO₃ + Ca(NO₃)₂ ⟶ CaCO₃ + 2 NaNO₃
By reaction stoichiometry (that is, the relationship between the amount of reagents and products in a chemical reaction), the following amounts of each compound participate in the reaction:
- Na₂CO₃: 1 mole
- Ca(NO₃)₂: 1 mole
- CaCO₃: 1 mole
- NaNO₃: 2 mole
Being the molar mass of the compounds:
- Na₂CO₃: 106 g/mole
- Ca(NO₃)₂: 164 g/mole
- CaCO₃: 100 g/mole
- NaNO₃: 85 g/mole
then by stoichiometry the following quantities of mass participate in the reaction:
- Na₂CO₃: 1 mole* 106 g/mole= 106 g
- Ca(NO₃)₂: 1 mole* 164 g/mole= 164 g
- CaCO₃: 1 mole* 100 g/mole= 100 g
- NaNO₃: 2 mole* 85 g/mole= 170 g
You can apply the following rule of three: if by stoichiometry 106 grams of Na₂CO₃ produce 100 grams of CaCO₃, 79.3 grams of Na₂CO₃ produce how much mass of CaCO₃?

mass of CaCO₃= 74.81 grams
<u><em>74.81 grams of calcium carbonate are produced from 79.3 g of sodium carbonate.</em></u>
Answer:
A. a magnet
Explanation:
Iron fillings could be separated from sand using a magnet
Since there's specific heat, you should use Q=mc△T. Depends on if this question also involves phase change or not, you might will need Lf (latent heat of fusion) or Lv (latent heat of vaporisation).