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3 years ago

30 points

2 answers:

8 0

The molecular weight for Calcium Chloride Dihydrate (CaCl2•2H20) is 2H2O.

mass of 64g/mol = 256.52 g/mol
mass of 11g/mol = 26.981538 g/mol
mass of 147g/mol= 146.9149 g/mol
258g/mol = 258.09843 g/mol

Tcecarenko [31]3 years ago

4 0

Answer:

$M=147.014 g/mol$

Explanation:

The atomic weights of the elements:

Ca=40.078 g/mol

Cl=35.453 g/mol

H=1.008 g/mol

O=15.999 g/mol

The calcium chloride dihydrate:

$M=(40.078+35.453*2+2*2*1.008+2*15.999)g/mol$

$M=147.014 g/mol$

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Given that ΔH = −571.6 kJ/mol for the reaction 2 H2(g) + O2(g) → 2 H2O(l), calculate ΔH for these reactions. (a) 2 H2O(l) → 2 H2

pashok25 [27]

Answer : The value of $\Delta H$ for the reaction is +571.6 kJ/mole.

Explanation :

According to Hess’s law of constant heat summation, the heat absorbed or evolved in a given chemical equation is the same whether the process occurs in one step or several steps.

According to this law, the chemical equation can be treated as ordinary algebraic expression and can be added or subtracted to yield the required equation. That means the enthalpy change of the overall reaction is the sum of the enthalpy changes of the intermediate reactions.

The given chemical reaction is,

$2H_2(g)+O_2(g)\rightarrow 2H_2O(l)$ $\Delta H_1=-571.6kJ/mole$

Now we have to determine the value of $\Delta H$ for the following reaction i.e,

$2H_2O(l)\rightarrow 2H_2(g)+O_2(g)$ $\Delta H_2=?$

According to the Hess’s law, if we reverse the reaction then the sign of $\Delta H$ change.

So, the value $\Delta H_2$ for the reaction will be:

$\Delta H_2=-(-571.6kJ/mole)$

$\Delta H_2=+571.6kJ/mole$

Hence, the value of $\Delta H$ for the reaction is +571.6 kJ/mole.

6 0

3 years ago

Democritus contributed to our understanding of the atom in which of the following ways?

Marianna [84]

I believe the answer is 3 - He hypothesized that all substances can be broken down into a smallest part called the atom.

7 0

3 years ago

Read 2 more answers

Calculate the molarity of a 17.5% (by mass) aqueous solution of nitric acid. Select one: a. 2.74 m b. 4.33 m c. 0.274 m d. 3.04

den301095 [7]

Answer:

Option e.

Explanation:

Molarity is the concentration that indicates moles of solute in 1 L of solution.

We have another concentration, percent by mass.

Percent by mass indicates mass of solute in 100 g of solution.

Our solute is HNO₃, our solvent is water.

17.5 g of nitric acid is the mass of solute. We can convert them to moles:

17.5 g . 1mol / 63g = 0.278 moles

We do not have volume of solution. We assume the mass is 100 g because the percent by mass but we need density to state the volume.

Density = Mass / Volume

Mass / Density = Volume

Once we have the volume, we need to be sure the units is in L, to determine molarity

M = mol /L

4 0

3 years ago

Cuales elementos tienen solo un electrón de valencia

aleksley [76]

Answer:

En el caso del sodio, la valencia es 1, ya que tiene un solo electrón de valencia, si pierde un electrón se queda con el último nivel completo.

Explanation:

Grupo de la tabla periódica Electrones de valencia

Grupo 14 (IV) (Grupo del carbono) 4

Grupo 15 (V) (Grupo del nitrógeno ) 5

6 0

3 years ago

When 0.49 g of a molecular compound was dissolved in 20.00 g of cyclohexane, the freezing point of the solution was lowered by 3

IRISSAK [1]

Answer: The molecular mass of this compound is 131 g/mol

Explanation:

Depression in freezing point:

$\Delta T_f=i\times k_f\times \frac{w_2\times 1000}{M_2\times w_1}$

where,

$\Delta T_f$ = depression in freezing point = $3.9^oC$

$k_f$ = freezing point constant = $20.8^0C/m$

m = molality

i = Van't Hoff factor = 1 (for non-electrolyte)

$w_2$ = mass of solute = 0.49 g

$w_1$ = mass of solvent (cyclohexane) = 20.00 g

$M_2$ = molar mass of solute = ?

Now put all the given values in the above formula, we get:

$(3.9)^oC=1\times (20.8^oC/m)\times \frac{(0.49g)\times 1000}{M_2\times (20.00g)}$

$M_2=131g/mol$

Therefore, the molar mass of solute is 131 g/mol

7 0

3 years ago