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 equation that correctly represent the reaction for formation of ammonia is

n2+ 3h2 → 2nh3 (answer d)

1 mole of nitrogen gas (n2) react with 3 moles of hydrogen gas (h2) to form 2 moles of ammonia ( nh3). this is in a process known as haber process were iron is used as a catalyst and reaction take place that a higher temperature and pressure. the process is exothermic hence energy is released.