Answer:
The enthalpy change for the given reaction is 424 kJ.
Explanation:
We have :
Enthalpy changes of formation of following s:
(standard state)
![\Delta H_{rxn}=\sum [\Delta H_f(product)]-\sum [\Delta H_f(reactant)]](https://tex.z-dn.net/?f=%5CDelta%20H_%7Brxn%7D%3D%5Csum%20%5B%5CDelta%20H_f%28product%29%5D-%5Csum%20%5B%5CDelta%20H_f%28reactant%29%5D)
The equation for the enthalpy change of the given reaction is:
=
=
The enthalpy change for the given reaction is 424 kJ.
Answer is: the mass of a block of magnesium is 177.75 grams.
m(Fe) = 826 g.
d(Fe) = 7.9 g/cm³.
1) Calculate volume of iron and magnesium:
d(Fe) = m(Fe) ÷ V(Fe).
V(Fe) = m(Fe) ÷ d(Fe).
V(Fe) = 826 g ÷ 7.9 g/cm³.
V(Fe) = V(Mg) = 104.56 cm³.
2) Calculate mass of magnesium:
m(Mg) = V(Mg) · d(Mg).
m(Mg) = 104.56 g/cm³ · 1.7 g/cm³.
m(Mg) = 177.75 g.
The answers are the following that can be answered using the chart:
A. Which type of hurricane is expected to strike more frequently this century?
Category 4 + 5C. In general, will hurricanes likely become stronger or weaker this century?
Stronger, because there are more stronger ones thant he weaker ones that can result to hurricane.
E. Which types of hurricanes are expected to drop in frequency by more than 25% this century?
Categories 1, 2, 3
Answer:
molecular weight (Mb) = 0.42 g/mol
Explanation:
mass sample (solute) (wb) = 58.125 g
mass sln = 750.0 g = mass solute + mass solvent
∴ solute (b) unknown nonelectrolyte compound
∴ solvent (a): water
⇒ mb = mol solute/Kg solvent (nb/wa)
boiling point:
- ΔT = K*mb = 100.220°C ≅ 373.22 K
∴ K water = 1.86 K.Kg/mol
⇒ Mb = ? (molecular weight) (wb/nb)
⇒ mb = ΔT / K
⇒ mb = (373.22 K) / (1.86 K.Kg/mol)
⇒ mb = 200.656 mol/Kg
∴ mass solvent = 750.0 g - 58.125 g = 691.875 g = 0.692 Kg
moles solute:
⇒ nb = (200.656 mol/Kg)*(0.692 Kg) = 138.83 mol solute
molecular weight:
⇒ Mb = (58.125 g)/(138.83 mol) = 0.42 g/mol
The question is incomplete, the complete question is;
The table above summarizes data given to a student to evaluate the type of change that took place when substance X was mixed with water. The student claimed that the data did not provide enough evidence to determine whether a chemical or physical change took place and that additional tests were needed. Which of the following identifies the best way to gather evidence to support the type of change that occurred when water and Xwere mixed?
A. Measuring the melting point of the mixture of water and X
B. Adding another substance to the mixture of water and X to see whether a solid forms
C Measuring and comparing the masses of the water, X, and the mixture of water and X
D Measuring the electrical conductivities of X and the mixture of water and X
Answer:
D Measuring the electrical conductivities of X and the mixture of water and X
Explanation:
Unfortunately, I am unable to reproduce the table here. However, from the table, the temperature of the of the mixture of the solid X and water was 101.6°C. This is above the boiling point of water and way below the temperature of the solid X.
This goes a long way to suggest that there was some kind of interaction between the water and X which accounted for the observed temperature of the system of X in water.
The only way we can be able to confirm if X actually dissolved in water is to measure the conductivity of the water. dissolved solids increase the conductivity of water.
