Explanation:
A physical change is one that alters the physical properties of matter (particularly the form and state).
A chemical change is one in which new kind of matter is formed. It is always accompanied by energy changes (evolution or absorption of energy in form of heat or light or both).
Now, the salient differences between physical and chemical changes;
- Physical changes are easily reversible whereas chemical changes are not easily reversible.
- Physical changes lead to the production of no new kinds of matter whereas chemical changes leads to the production of new kinds of matter.
- Physical changes involves no change in mass whereas chemical changes involves change in mass.
- Physical changes require little energy whereas considerable amount of energy is needed for chemical changes.
Complete question is;
A drop of water has a volume of approximately 7 × 10⁻² ml. How many water molecules does it contain? The density of water is 1.0 g/cm³.
This question will require us to first find the number of moles and then use avogadro's number to get the number of water molecules.
<em><u>Number of water molecules = 2.34 × 10²¹ molecules</u></em>
We are given;
Volume of water; V = 7 × 10⁻² ml
Density of water; ρ = 1 g/cm³ = 1 g/ml
Formula for mass is; m = ρV
m = 1 × 7 × 10⁻²
m = 7 × 10⁻² g
from online calculation, molar mass of water = 18.01 g/mol
Number of moles(n) = mass/molar mass
Thus;
n = (7 × 10⁻²)/18.01
n = 3.887 × 10⁻³ mol
from avogadro's number, we know that;
1 mol = 6.022 × 10²³ molecules
Thus,3.887 × 10⁻³ mol will give; 6.022 × 10²³ × 3.887 × 10⁻³ = 2.34 × 10²¹ molecules
Read more at; brainly.in/question/17990661
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Answer:
13mL
Explanation:
Step 1:
The balanced equation for the reaction. This is given below:
HNO3 + KOH —> KNO3 + H2O
From the balanced equation above, we obtained the following data:
Mole ratio of the acid (nA) = 1
Mole ratio of the base (nB) = 1
Step 2:
Data obtained from the question.
This includes the following:
Molarity of the acid (Ma) = 6M
Volume of the acid (Va) =?
Volume of the base (Vb) = 39mL
Molarity of the base (Mb) = 2M
Step 3:
Determination of the volume of the acid.
Using the equation:
MaVa/MbVb = nA/nB, the volume of the acid can be obtained as follow:
MaVa/MbVb = nA/nB
6 x Va / 2 x 39 = 1/1
Cross multiply to express in linear form
6 x Va = 2 x 39
Divide both side by 6
Va = (2 x 39)/6
Va = 13mL
Therefore, the volume of the acid (HNO3) needed for the reaction is 13mL
