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Shkiper50 [21]
3 years ago
9

Which of these statements are true? Select all that apply.

Chemistry
2 answers:
Anarel [89]3 years ago
4 0
In order to find the two statements, we must first define what the enthalpy of formation and the enthalpy of reaction mean.

Enthalpy of formation:
The change in enthalpy when one mole of substance is formed from its constituent elemetns at standard state.

Enthalpy of reaction:
The change in enthalpy when a reaction occurs and the reactants and products are in their standard states.

Now, we check the statements. The true ones are:

The Hrxn for C(s) + O₂(g) → CO₂(g) is the same as Hf for CO₂
This is true because the formation of carbon dioxide requires carbon and oxygen in their standard states.

T
he Hf for Br₂<span>(l) is 0 kJ/mol by definition.
Because the bromine is present in its standard state, the enthalpy of formation is 0.

</span><span>The Hrxn for the reaction 1.5H</span>₂<span>(g) + 0.5N</span>₂<span>(g) </span>→ <span>NH</span>₃<span>(g) is the same as the Hf for NH</span>₃<span>(g)
The reactants and products are present in their standard state, and the reaction is the same as the one occurring during the formation of ammonia.
</span>
morpeh [17]3 years ago
3 0

Answer:

1,3,6

Explanation:

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Jlenok [28]
D. Liquid Nitrogen is much colder than Water.
5 0
3 years ago
Which is the next logical step in balancing the given equation? 3CO(g) + Fe2O3(s) Fe(s) + 3CO2(g)
Elena-2011 [213]

I believe that the answer is A.

5 0
3 years ago
Read 2 more answers
20 mL of an approximately 10% aqueous solution of ethylamine, CH3CH2NH2, is titrated with 0.3000 M aqueous HCl. Which indicator
Eduardwww [97]

Answer:

Therefore, The indicator that is best fit for the given titration is Bromocresol Green Color change from pH between 4.0 to 5.6

Bromocresol green, color change from pH = 4.0 to  5.6

Explanation:

The equation for the reaction is :

C_2H_5NH_2_(_a_q_)     +     H^+_(_a_q_)   ---      C_2H_5NH_{3(aq)}^+

concentration of C_2H_5NH_{2(aq) = 10%

10 g of C_2H_5NH_{2(aq) in 100 ml solution

molar mass = 45.08 g/mol

number of moles = 10 / 45.08

= 0.222 mol

Molarity of C_2H_5NH_2(aq) = 0.222 \times \frac{1000}{100}mL

= 2.22 M

number of moles of C_2H_5NH_{2(aq) in 20 mL can be determined as:

= 20 mL \times  2.22 M= 44*10^{-3} mole

Concentration of C_2H_5NH_2(aq) = \frac{44*10^{-3}*1000}{20}

= 2.22 M

Similarly, The pKa Value of C_2H_5NH_{2(aq) is given as 10.75

pKb value will be: 14 - pKa

= 14 - 10.75

= 3.25

the pH value at equivalence point is,

pH= \frac{1}{2}pKa - \frac{1}{2}pKb-\frac{1}{2}log[C]

pH = \frac{14}{2}-\frac{3.25}{2}-\frac{1}{2}log [2.22]

pH = 5.21

Therefore, The indicator that is best fit for the given titration is Bromocresol Green Color change from pH between 4.0 to 5.6

8 0
3 years ago
Calculate the number of O atoms in 0.150 g of CaSO4 · 2H2O.
natulia [17]

Answer:

There are 0.00523 moles of oxygen in 0.150 grams of calcium sulfate crystal.

Explanation:

Mass of calcium sulfate crystal = m = 0.150 g

Molar mass of calcium sulfate crystal = M = 172 g/mol

Moles of magnesium nitrate = n

n=\frac{m}{M}

n=\frac{0.150 g}{172 g/mol}=0.0008721 mol

1 mole of calcium sulfate crystal has 6 moles of oxygen atoms. Then 0.004446 moles calcium sulfate crystal will have :

6\times 0.0008721 mol=0.0052326mol\approx 0.00523 mol

There are 0.00523 moles of oxygen in 0.150 grams of calcium sulfate crystal.

8 0
3 years ago
7. What is the prefix value for 100X?
Lilit [14]

Answer:

hecto-

Explanation:

The prefix value of 100 is hecto therefore 100X can be called hecto-x.

Such prefixes as this are expressed in the order of tens. Units generally exists scientifically in multiples and submultiples form using prefixes.

For the multiples:

             10                            deca(da)

            100                           hecto(h)

            1000                        kilo(k)

         1000000                    mega(M)

         1000000000            giga(G)

4 0
3 years ago
Read 2 more answers
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