Physical changes occur when the properties of a substance are retained and/or the materials can be recovered after the change. Chemical changes involve the formation of a new substance. Formation of a gas, solid, light, or heat are possible evidence of chemical change.
Answer:
(a) Constitutional Isomers
(b) Constitutional Isomers
Explanation:
Constitutional isomers are also known with the name Structural Isomers. These are the compounds which have same chemical formula but differ in arrangement of atoms i.e. structure.
Both the compounds <em>cis-1,3-dibromocyclohexane</em> and <em>trans-1,4-dibromocyclohexane</em> have the same chemical formula 
but have different structure as shown in the image below.
In the second case the compounds <em>2,3-dimethylhexane</em> and <em>2,3,3-trimethylpentane</em>, both have same chemical formula 
but have different structures which is shown in the image below.
Thus it is clear that in both the groups (a) and (b) the given compounds are Constitutional Isomers.
The value of X is 10 hence the formula of unknown hydrate sodium sulfate is NaSO4.10 H20
calculation
step 1:find the moles of NaSO4 and the moles of H2O
moles= mass/molar mass
moles of Na2SO4=1.42÷142=0.01 moles
moles of H20= mass of H2O/molar mass of H2O
mass of H2O= 3.22-1.42=1.8g
mole of H2O is therefore 1.8÷18=0.1 moles
step 2: find the mole ratio by dividing each mole by smallest number of mole (0.01)
that is Na2So4= 0.01/0.01 =1
H2O= 0.1/0.01=10
Na₂S(aq) + Cd(NO₃)₂(aq) = CdS(s) + 2NaNO₃(aq)
v=25.00 mL
c=0.0100 mmol/mL
M(Na₂S)=78.046 mg/mmol
n(Na₂S)=n{Cd(NO₃)₂}=cv
m(Na₂S)=M(Na₂S)n(Na₂S)=M(Na₂S)cv
m(Na₂S)=78.046*0.0100*25.00≈19.5 mg
Answer:
NaI > Na2SO4 > Co Br3
meaning that NaI has the highest freezing point, and Co Br3 has the lowest freezing point.
Explanation:
The freezing point depression is a colligative property.
That means that it depends on the number of solute particles dissolved.
The formula to calculate the freezing point depression of a solution of a non volatile solute is:
ΔTf = i * Kf * m
Where kf is a constant, m is the molality and i is the van't Hoff factor.
Molality, which is number of moles per kg of solvent, counts for the number of moles dissolved and the van't Hoff factor multipllies according for molecules that dissociate.
The higher the number of molecules that dissociate, the higher the van't Hoff, the greater the freezing point depression and the lower the freezing point.
As the question states that you assume equal concentrations (molality) and complete dissociation you just must find the number of ions generated by each solute, in this way:
NH4 I → NH4(+) + I(-) => 2 ions
Co Br3 → Co(+) + 3 Br(-) => 4 ions
Na2SO4 → 2Na(+) + SO4(2-) => 3 ions.
So, Co Br3 is the solute that generate more particles and that solution will exhibit the lowest freezing point among the options given, Na2SO4 is next and the NaI is the third. Ordering the freezing point from higher to lower the rank is NaI > Na2SO4 > CoBr3, which is the answer given.
