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2 years ago

How many kilojoules are needed to convert 77.5 grams of ice at -8.00°C to water at 95.0°C?

Chemistry

1 answer:

Over [174]2 years ago

7 0

Q=mcθ
m= 0.0775 kg
c= 4184 J·kg−1·K−1.
θ= T(final) - T(initial), 95-(-8)

Q=33398.78 J so kJ divide 1000

= 33.39878 kJ

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Nitrogen and hydrogen combine to form ammonia in the Haber process. Calculate (in kJ) the standard enthalpy change ΔH° for the r

PolarNik [594]

Answer: -105 kJ

Explanation:-

The balanced chemical reaction is,

$N_2(g)+3H_2(g)\rightarrow 2NH_3(g)$

The expression for enthalpy change is,

$\Delta H=\sum [n\times B.E(reactant)]-\sum [n\times B.E(product)]$

$\Delta H=[(n_{N_2}\times B.E_{N_2})+(n_{H_2}\times B.E_{H_2}) ]-[(n_{NH_3}\times B.E_{NH_3})]$

$\Delta H=[(n_{N_2}\times B.E_{N\equiv N})+(n_{H_2}\times B.E_{H-H}) ]-[(n_{NH_3}\times 3\times B.E_{N-H})]$

where,

n = number of moles

Now put all the given values in this expression, we get

$\Delta H=[(1\times 945)+(3\times 432)]-[(2\times 3\times 391)]$

$Delta H=-105kJ$

Therefore, the enthalpy change for this reaction is, -105 kJ

8 0

3 years ago

How many grams of NaOH are<br> needed to make 400. mL of<br> 1.50 M solution?

juin [17]

Answer:

24g of NaOH are required

Explanation:

Molarity, M, is an unit of concentration widely used in chemistry defined as the ratio between moles of solute (In this case, NaOH), and volume of solution in liters.

We can find the moles of NaOH and its mass with the volume and desired concentration as follows:

<em>Moles NaOH:</em>

400.0mL = 0.400L * (1.50mol / L) = 0.600 moles NaOH

<em>Mass NaOH -Molar mass: 40.0g/mol-:</em>

0.600 moles * (40.0g / mol) =

<h3>24g of NaOH are required</h3>

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3 years ago

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lana [24]

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3 years ago