This is seen in the first law of Thermodynamics stating that matter and energy cannot be destroyed nor created.
I haven't got the answer but I'm probably sure that u can actually look up that answer hoped it help
Answer:

Explanation:
Hello,
In this case, since the density is defined as the ratio between the mass and the volume as shown below:

We can compute the density of water for the given 43 g that occupy the volume of 43 mL:

Regards.
Cu(s) + 2 AgNO3 = Cu(NO3)2 + 2 Ag 63.5 g Cu ---------------- 2 x 169.87 g AgNO3 ( mass Cu ?) -------------- 4.00 g AgNO3 mass Cu = 4.00 x 63.5 / 2 x 169.87 mass Cu = 254 / 339.74 = 0.747 g of Cu
Hope this helps
The chemical formula : X₃Y₂
<h3>Further explanation </h3>
The noble gas element is a stable class of elements. The noble gas element is monatomic. Stability of noble gases is caused by an electron configuration that has a stable configuration of 8 (has 8 valence electrons) except He with a duplet configuration (has 2 valence electrons)
Other elements that do not yet have electron configurations such as noble gases will try to achieve their stability by forming bonds between elements.
This is generally called the octet rule
X has 2 valence electrons.to achieve stability, element X will release 2 electrons to form X²⁺
Y has 5 valence electrons, to achieve stability, the element Y will attract/ add electrons to form Y³⁻
The two compounds will form a compound with the charges crossed : X₃Y₂