As with the properties of a substance, the changes that substances undergo can be classified as either physical or chemical. During physical changes a substance changes its physical appearance, but not its composition. The evaporation of water is a physical change.
(I searched that up but here’s an explanation with my own words that you can use):
Change in matter can be classified as a physical change as well as a chemical change due to the properties of substance. A physical change changes substance within its appearance but not its composition. For an example: The evaporation of water is a physical change.
There you go hopefully that helped
The molarity of KOH is 0.1055 M
<u><em> calculation</em></u>
Step 1: write the equation for reaction between H₂C₂O₄.2H₂O and KOH
H₂C₂O₄.2H₂O + 2 KOH → K₂C₂O₄ +4 H₂O
step 2: find the moles of H₂C₂O₄.2H₂O
moles = mass÷ molar mass
from periodic table the molar mass H₂C₂O₄.2H₂O= (1 x2) +(12 x2) +(16 x4) + 2(18)=126 g/mol
= 0.2000 g ÷ 126 g/mol =0.00159 moles
step 3: use the mole ratio to calculate the moles of KOH
H₂C₂O₄.2H₂O : KOH is 1:2
therefore the moles of KOH =0.00159 x 2 = 0.00318 moles
step 4: find molarity of KOH
molarity = moles/volume in liters
volume in liters = 30.12/1000=0.03012 L
molarity is therefore = 0.00318/0.03012 =0.1055 M
Molecular weight of (NH4)2 CO3 = 96 gm. 96 gm (NH4)2CO3 = 1 mol of (NH4)2CO3 = 2 moles of NH4.
Therefore 1.3 gm of (NH4)2CO3 = 1.3x2/ 96 = 0.027 moles.
