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3 years ago

100.0 g water cools from 85.0°C to 20.0°C. If the specific heat of water is 4.18 J/g°C, calculate the change in energy.

Chemistry

1 answer:

Natali5045456 [20]3 years ago

5 0

Answer:

-27.2 kJ

Explanation:

We can use the heat-transfer formula. Recall that:

$\displaystyle q = mC\Delta T$

Where m is the mass, C is the substance's specific heat, and ΔT is the change in temperature.

Hence substitute:

$\displaystyle \begin{aligned} q & = (100.0\text{ g})\left(\frac{4.18\text{ J}}{\text{g-$^\circ$C}}\right)(20.0\text{ $^\circ$C} - 85.0\text{ $^\circ$C}) \\ \\ & =(100.0\text{ g})\left(\frac{4.18\text{ J}}{\text{g-$^\circ$C}}\right)(-65.0\text{ $^\circ$C}) \\ \\ & = -2.72\times 10^4\text{ J} = -27.2\text{ kJ}\end{aligned}$

Therefore, the cooling of the water released about 27.2 kJ of heat.

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1N2 + 3H2 -->

Hunter-Best [27]

Answer:

28.23 g NH₃

Explanation:

The balanced chemical equation is:

N₂(g) + 3 H₂(g) → 2 NH₃(g)

Thus, 1 mol of N₂ reacts with 2 moles of H₂ to produce 2 moles of NH₃. We convert the moles to mass (in grams) by using the molecular weight (MW) of each compound:

MW(N₂) = 2 x 14 g/mol = 28 g/mol

mass N₂= 1 mol x 28 g/mol = 28 g

MW(H₂) = 2 x 1 g/mol = 2 g/mol

mass H₂ = 3 mol x 2 g/mol = 6 g

MW(NH₃) = 14 g/mol + (3 x 1 g/mol) = 17 g/mol

mass NH₃= 2 moles x 17 g/mol = 34 g

Now, we have to figure out which is the limiting reactant. For this, we know that the stoichiometric ratio is 28 g N₂/6 g H₂. If we have 36.85 g of H₂, we need the following mass of N₂:

36.85 g H₂ x 28 g N₂/6 g H₂ = 171.97 g N₂

We have 23.15 g N₂ and we need 171.97 g. So, we have lesser N₂ than we need. Thus, the limiting reactant is N₂.

Now, we calculate the product (NH₃) by using the stoichiometric ratio 34 g NH₃/28 g N₂, with the mass of N₂ we have:

23.25 g N₂ x 34 g NH₃/28 g N₂ = 28.23 g NH₃

Therefore, the maximum amount of NH₃ that can be produced is 28.23 grams.

5 0

3 years ago

Describe at least two ways that a researcher can minimize experimental errors in an investigation.

Leto [7]

Experimental errors can be of two kinds: human error and analytical error. Analytical error can be corrected easily. You just have to use instruments that are of high precision. For example, instead of using the platform balance, use the analytical balance which displays 4 decimal places to be highly accurate. For the human error, this is subjective. The only way to correct human error is to be more meticulous on your data measurements.

8 0

3 years ago

Ain___accepts electrons and becomes___

Serga [27]

Answer:

An atom accepts electrons and becomes an anion.

Explanation:

Atomic number = number of electrons = number of protons.

Atomic number of sodium is 11

So the atom contains 11 protons and 11 electrons

To find the number of neutrons we make use of the formula

Mass number - atomic number = number of neutrons

From the periodic table, we know mass number of sodium is 23

So number of neutron = 23 - 11 = 12.

When a sodium atom loses an electron it will have 11 positive protons and 10 negative electrons. Since 1 positive charge is more, Na becomes $Na^+$ .