Answer:
5.42 mol
Explanation:
To find moles, divide the given mass by the compounds molar mass. To find the molar mass of the compound, add of the masses of each individual component:
Molar mass of NaNCO3 = Na + N + C + (O x 3)
Molar mass of NaNCO3 = 23 + 14 + 12 + (16 x 3)
Molar mass of NaNCO3 = 97 g/mol
Moles = mass / molar mass
Moles = 526 g / 97 g/mol
Moles = 5.42 mol
Answer:
1.0 × 10⁸ ruthenium atoms
Explanation:
Step 1: Calculate the diameter (d) of an atom of ruthenium
The diameter of an atom is twice its radius.
d = 2 × r = 2 x 178 pm = 356 pm
Step 2: Convert "d" to meters
We will use the conversion factor 1 m = 10¹² pm.
356 pm × 1 m/10¹² pm = 3.56 × 10⁻¹⁰ m
Step 3: Convert the distance of the tip of a finger (D) to meters
We will use the conversion factor 1 m = 10² cm.
3.6 cm × 1 m/10² cm = 0.036 m
Step 4: Calculate the number of atoms of ruthenium required
We will use the following expression.
D/d = 0.036 m/3.56 × 10⁻¹⁰ m = 1.0 × 10⁸
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Answer:
Example A describes a physical change and Example B describes a chemical change.
Explanation:
Physical Change
The changes that occur only due to change in shape or physical properties but their chemical or internal composition remain unchanged.
These changes were reversible.
They have same chemical property.
These changes can be observed with naked eye.
Example :
Vegetables are chopped and converted into smaller pieces the composition remain same. It is physical change.
Water converting to Ice
Water converting to gas
In this water molecule remain the same only they rearrange themselves that change its state of mater not composition
Chemical change:
The changes, that occur due to change in the composition of a substance and result in a different compound is known as chemical change.
These changes are irreversible
These changes occur due to chemical reactions
These may not be observed with naked eye
Example:
Combustion of fuel or wood: that oil or wood convert into energy, CO2 and ash in case of wood
Boiling of egg: that change the chemical composition of protein in the egg .
Food is broken up into simpler form during digestion and convert into the energy and particles which are different from original compound .
times concentration OH-
