Hi I'm in Chemistry too this year,
I believe D is correct because usually physical changes are things like density, color or quantity.
Answer:

Explanation:
Hello,
In this case, the undergoing chemical reaction is:

Thus, given the 1.00-kg of 12.5% ore, we can compute the theoretical yield of copper (II) oxide via stoichiometry:

Whereas the third factor accounts for the percent purity of the covellite. Then, given the percent yield, we can compute the actual yield by:

Regards.
Answer: 11.0 g of calcium will react with 10.0 grams of water.
Explanation:
To calculate the moles, we use the equation:
moles of
The balanced chemical equation is:
According to stoichiometry :
2 moles of
require = 1 mole of
Thus 0.55 moles of
require=
of
Mass of
Thus 11.0 g of calcium will react with 10.0 grams of water.
Answer:
KBr
Explanation
KBr is an ionic compound which have very high BP since they exist as 3D crystals
Methyl Bromide, CH3Br. is a covalent compound which have low BP since they exist as individual molecules
Answer:
Explanation:
100mL = 0.1L
0.55 M = mol/0.1 L
mol = 0.055 mol
molar mass of KI = 165.998 g
0.055 * 165.998 = 9.13 g of KI