Nothing happens because a physical change only changes the appearance of the substance, whereas a chemical change transforms the substance into something completely different.
i.e. (chemical change) wood + fire = ash
(physical change) wood + axe = smaller pieces of wood
Explanation:
The law of conservation of mass states that the total mass of the products is equal to the total of the reactants.
A chemical change occurs because of a chemical reaction.
In a chemical reaction, the reactants are the starting substances and the products is the finishing substances. The amount of each type of atoms to start with and end with are also equal.
No matter disappears after a chemical reaction.
Answer:
The amount of matter in the new substances is the same as the original.
This is known as the law of conservation of mass.
Question:
<span>A sample of nitrogen gas had a volume of 500mL, a pressure in its closed container of 740 torr and a temperature of 25°c. what was the volume of gas when the temperature was changed to 50°c and the new pressure was 760 torr?
Answer:
Data Given:
V</span>₁ = 500 mL
P₁ = 740 torr
T₁ = 25 °C + 273 = 298 K
V₂ = ?
P₂ = 760 torr
T₂ = 50 °C + 273 = 323 K
Solution:
Let suppose the gas is acting Ideally, then According to Ideal Gas Equation,
P₁ V₁ / T₁ = P₂ V₂ / T₂
Solving for V₂,
V₂ = (P₁ V₁ T₂) ÷ (T₁ P₂)
Putting Values,
V₂ = (740 torr × 500 mL × 323 K) ÷ (298 K × 760 torr)
V₂ = 527.68 mL
C. A central body is the center of the universe.
Answer:
2.04 x 10²⁴ molecules
Explanation:
Given parameters:
Mass of Be(OH)₂ = 145.5g
To calculate the number of molecules in this mass of Be(OH)₂ we follow the following steps:
>> Calculate the number of moles first using the formula below:
Number of moles = mass/molarmass
Since we have been given the mass, let us derive the molar mass of Be(OH)₂
Atomic mass of Be = 9g
O = 16g
H = 1g
Molar Mass = 9 + 2(16 + 1)
= 9 + 34
= 43g/mol
Number of moles = 145.5/43 = 3.38mol
>>> We know that a mole is the amount of substance that contains Avogadro’s number of particles. The particles can be atoms, molecules, particles etc. Therefore we use the expression below to determine the number of molecules in 3.38mol of Be(OH)₂:
Number of
molecules= number of moles x 6.02 x 10²³
Number of molecules= 3.38 x 6.02 x 10²³
= 20.37 x 10²³ molecules
= 2.04 x 10²⁴ molecules
