Select the correct statement to describe when a sample of liquid water vaporizes into water vapor.

bagirrra123 [75]

$176.0 \; \text{kJ} \cdot \text{mol}^{-1}$

As long as the equation in question can be expressed as the sum of the three equations with known enthalpy change, its $\Delta H$ can be determined with the Hess's Law. The key is to find the appropriate coefficient for each of the given equations.

Let the three equations with $\Delta H$ given be denoted as (1), (2), (3), and the last equation (4). Let $a$ , $b$ , and $c$ be letters such that $a \times (1) + b \times (2) + c \times (3) = (4)$ . This relationship shall hold for all chemicals involved.

There are three unknowns; it would thus take at least three equations to find their values. Species present on both sides of the equation would cancel out. Thus, let coefficients on the reactant side be positive and those on the product side be negative, such that duplicates would cancel out arithmetically. For instance, $3 + (-1) = 2$ shall resemble the number of $\text{H}_2$ left on the product side when the second equation is directly added to the third. Similarly

$\text{NH}_4 \text{Cl} \; (s)$ : $-2 \; a = 1$
$\text{NH}_3\; (g)$ : $-2 \; b = -1$
$\text{HCl} \; (g)$ : $2 \; c = -1$

Thus

$a = -1/2\\b = 1/2\\c = -1/2$ and

$-\frac{1}{2} \times (1) + \frac{1}{2} \times (2) - \frac{1}{2} \times (3)= (4)$

Verify this conclusion against a fourth species involved- $\text{N}_2 \; (g)$ for instance. Nitrogen isn't present in the net equation. The sum of its coefficient shall, therefore, be zero.

$a + b = -1/2 + 1/2 = 0$

Apply the Hess's Law based on the coefficients to find the enthalpy change of the last equation.

$\Delta H _{(4)} = -\frac{1}{2} \; \Delta H _{(1)} + \frac{1}{2} \; \Delta H _{(2)} - \frac{1}{2} \; \Delta H _{(3)}\\\phantom{\Delta H _{(4)}} = -\frac{1}{2} \times (-628.9)+ \frac{1}{2} \times (-92.2) - \frac{1}{2} \times (184.7) \\\phantom{\Delta H _{(4)}} = 176.0 \; \text{kJ} \cdot \text{mol}^{-1}$

3 0

3 years ago

Using logarithms, you determined the A)Solubility B)Temperatures C)ph

dem82 [27]

Answer:

the answer is pH

Explanation:

Just took it on ed2020

7 0

3 years ago

Hellllppppp lons Worksheet

Iteru [2.4K]

The metals will lose electrons while the non metals will gain electrons in order to attain octet structure.

An ion can be cation (positively charged) or anion (negatively charged).

Cations attain octet structure (8) by losing electron(s) while anions become stable or attains octet structure (8) by gaining electron(s).

The remaining elements are completed as follows to attain octet structure;

Element--valence electron--electrons to gain--electrons to lose--ion formed

O ------------ 6 ---------------------- 2 ------------------------ none -------------- $O^{2-}$

Ca -------- 2 ----------------------- none ---------------------- 2 ------------------ $Ca^{2+}$

Br ----------- 7 --------------------- 1 ------------------------ none --------------- $Br^{-}$

S ------------ 6 ----------------------- 2 ------------------------ none --------------- $S^{2-}$

Cl ------------ 7 ----------------------- 1 ------------------------ none ---------------- $Cl^{-}$

K -------------- 1 ----------------------- none ----------------------- 1 ------------------ $K^{+}$

Mg ------------ 2 ---------------------- none ---------------------- 2 ---------------- $Mg^{2+}$

Be ------------- 2 ---------------------- none ---------------------- 2 ---------------- $Be^{2+}$

Learn more here: brainly.com/question/21089350

8 0

3 years ago

The volume of an irregular solid can be found from its displacement in a known volume of water.

Eva8 [605]

Answer:

The volume of an irregularly shaped solid can be determined from the volume of water it displaces. A graduated cylinder contains 19.9 mL of water. When a small piece of galena is added, it sinks and the volume increases to 24.5 mL

4 0

3 years ago

A calorimeter contains 500 g of water at 25°C. You place a hand warmer containing 100 g of liquid sodium acetate (NaAC) inside t

antoniya [11.8K]

The heat absorbed by the water is
Q = 500 (4.18) (32.2 - 25)
Q = 15048 J

The enthalpy of fusion of the sodium acetate is:
ΔHf = Q / m
ΔHf = 15048 / 100
ΔHf = 150.48 J/g

3 0

3 years ago

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