1. The student didn’t push with enough force ._.
1.5 % is the percent yield in the reaction.
Explanation:
Given that:
original mass of the sample used in reaction = 1.897 grams
product formed after decomposition = 1.071 grams
The reaction for the decomposition:
Mg(HCO3)2 (s) ⇒ CO2 (g) + H2O (g) + MgCO2 (s)
It says that 1 mole of Mg(HCO3)2 yielded 1 mole of MgCO2 on decomposition
68.31 grams/mole or 68.31 grams of MgCO2 is formed
percent yield =
x 100
putting the values in the equation:
percent yield = 
= 0.015 x100
PERCENT YIELD = 1.5 %
V1/T1=V2/T2
524 cm^3/491 K =V2/297K
V2=(524 cm^3*297K)/491 K= 317K
If you count the number of electrons (small dots), you have the atomic number. In this case you have 11 so this atom is a sodium atom. Sodium has 1 valence electron (electron on the outer shell) and chlorine has 7. This means that if sodium gave one electron away and chlorine would obtain one electron, they would both have the (ideal) noble gas conformation (full outer shell).