Burning a magnesium ribbon in the air is an addition reaction while heating potassium manganate 7 is a decomposition reaction.
<h3>Addition and decomposition reactions</h3>
Magnesium burns in air to produce magnesium oxide as follows:

Potassium manganate 7 burns to produce multiple products as follows:

Thus, the MgO will be heavier than Mg. On the other hand,
will be less heavy than
.
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The partial pressure of methane in the mixture of methane and ethane has been 1 atm.
Partial pressure has been the pressure exerted by a gas in the solution or mixture. The partial pressure of each gas has been the total pressure of the gaseous mixture.
The partial pressure of the gas has been dependent on the volume, temperature, and concentration of the gas.
The given methane has a partial pressure of 1 atm in the 15 L vessel. The addition of ethane results in the change in the total pressure of the mixture, as there have been additional moles of solute that contributes to the solution pressure.
However, since there has been no change in the concentration and volume of methane, the pressure exerted by methane has been the same. Thus, the partial pressure of methane has been 1 atm.
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Answer: similar, energy
Explanation: (edmentum answer) Several of the elements in period 5 have electron configurations with only one electron in the 5s sublevel. That suggests that the next sublevel that electrons typically fill, 4d, is not much higher in energy.