Total weight of the mixture of sand and salt = 5.25 g
Weight of sand separated = 3.64 g
Weight of the salt in the mixture = (5.25 - 3.64) g
= 1.61 g
Then the percentage of sand in the sample = [(3.64/5.25) * 100] percent
= 69.33%
So the percentage of sand in the total mixture of sand and salt is 69.33%.
Answer:
Bonds are broken and new bonds are formed during chemical reactions only.
Explanation:
- A physical change in a substance doesn't change what the substance is.
- In a chemical change where there is a chemical reaction, a new substance is formed and energy is either given off or absorbed.
- Physical changes can be reversed, chemical changes cannot be reversed with the substance changed back without extraordinary means, if at all. For example, a cup of water can be frozen when cooled and then can be returned to a liquid form when heated.
So, the right choice is:
Bonds are broken and new bonds are formed during chemical reactions only.
4,561.245 Joules
Q = Mass x Change in Temperature x Specific Heat
Q = 22.6 x 225 x .897
Answer:
38.541 × 10¹⁹ formula units
Explanation:
Given data:
Mass of chromium sulfate = 0.25 g
Formula units in 0.25 g = ?
Solution:
The given problem will solve by using Avogadro number.
It is the number of atoms , ions and molecules in one gram atom of element, one gram molecules of compound and one gram ions of a substance.
The number 6.022 × 10²³ is called Avogadro number.
For example,
18 g of water = 1 mole = 6.022 × 10²³ formula units of water
Number of moles of chromium sulfate = Mass / molar mass
Number of moles of chromium sulfate = 0.25 g/ 392.16 g/ mol
Number of moles of chromium sulfate = 6.4 × 10⁻⁴ moles
Number of formula units:
1 mole = 6.022 × 10²³ formula units
6.4 × 10⁻⁴ moles × 6.022 × 10²³ formula units / 1 mol
38.541 × 10¹⁹ formula units
