A20.69 g sample of impure magnesium car- bonate was heated to complete decomposition according to the equation mgco3(s) → mgo(s) + co2(g) . after the reaction was complete, the solid residue (consisting of mgo and the original impurities) had a mass of 17.48 g. assum- ing that only the magnesium carbonate had decomposed, what was the percent of magne- sium carbonate in the original sample? answer in units of %.

Explanation:

We will need an equation with molar masses, so let’s gather all the information in one place.  

M_r:     84.31                    44.01

          MgCO₃ ⟶ MgO + CO₂

The mass lost was that of CO₂.

1. Mass of CO₂

Mass of CO₂ = 20.69 g - 17.48 g = 3.21 g CO₂

2. Moles of CO₂

3. Moles of MgCO₃

The molar ratio is 1 mol MgCO₃:1 mol CO₂

4. Mass of MgCO₃

5. % MgCO₃

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.