Closed system. If the system is not closed, matter or energy can escape from the system. an example of this is if you react magnesium and hydrochloric acid in a open system. The H₂ gas is going to escape making it look like some of the mass disappeared . in that same reaction some in an open system will also loose heat to the surrounding which will make it look like less heat was produced.
Answer: 
Explanation:
Depression in freezing point is given by:
= Depression in freezing point
i= vant hoff factor = 1 (for non electrolyte like urea)
= freezing point constant = 
m= molality
Weight of solvent (X)= 950 g = 0.95 kg
Molar mass of non electrolyte (urea) = 60.06 g/mol
Mass of non electrolyte (urea) added = ?
Thus urea was dissolved.
Answer:
2H2+O2->2H2O
Explanation:
You have to balance the equation, you have 4 hydrogen and 2 oxygen atoms
Answer:
Humus, which ranges in colour from brown to black, consists of about 60 percent carbon, 6 percent nitrogen, and smaller amounts of phosphorus and sulfur. As humus decomposes, its components are changed into forms usable by plants.
samira-
Answer:
D) HCOOCH2CH3
Explanation:
An isomer of a compound is defined as a chemical substances with the same formula (That is, same atoms) but in different structures.
For propanoic acid, there are <em>3 atoms of C, 6 atoms of H and 2 atoms of oxygen.</em>
A) CH2CHCOOH
. Here you have 3 atoms of C but 4 atoms of H. That means this compound is not an isomer.
B) CH3CH2CH2COOH
. Here, there are 4 atoms of C. Thus, is not an isomer.
C) CH3CH(OH)CH2OH. This structure has 3 atoms of C, but 8 atoms of H. Thus, is not an isomer.
D) HCOOCH2CH3. Here, there are 3 atoms of C, 6 atoms of H and 2 atoms of O. Thus, this structure <em>is an isomer of propanoic acid.</em>
