Science

[razorback]

mass of crucible alone = 10.5 g
mass of crucible + magnesium ribbon = 11.7 g
mass of crucible and contents after heating = 13.3 g

calculate the mass of magnesium that was burned
calculate the mass of oxygen that reacted with the magnesium
calculate the mass of magnesium oxide that formed in the crucible

a stream of white smoke came out of the crucible as the magnesium was heating how would this affect the contents of the crucible after heating.

[fiction-factory]

As a first step you need to look at the formula for the reaction

[fiction-factory]

The weight of the magnesium prior to the reaction will probably get you an easy mark.

[fiction-factory]

>calculate the mass of magnesium oxide that formed in the crucible

Isn't that just a simple subtraction as well?

[fiction-factory]

Ignore the last bit- there may still be some magnesium left in there

[EDDIE51]

Basic 1st year chemistry
Mass of Magnesium burned 11.7 - 10.5 = 1.2g
Mass of Magnesium Oxide 13.3 -10.5 = 2.8g
Mass of Oxygen that reacted 2.8 - 1.2 =1.6g
You assume all the Magnesium has burnt .

[EDDIE51]

The white smoke was some of the Magnesium Oxide being lost as smoke so the result will be low.
In reality a crucible with a well fitting lid is used so there is no loss.