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2 years ago

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A student noticed a yellow, solid substance was formed when mixing two clear liquids during a lab. What term describes this yell

ow, solid substance?
A. physical change
B. exothermic reaction
C. endothermic reaction
D. precipitate

1 answer:

givi [52]2 years ago

5 0

Answer:

D

Explanation:

a precipitate is formed from a solution

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The decomposition of copper(II) nitrate on heating is endothermic reaction. 2Cu(NO3)2(s) → 2C10(s) + 4NO2(g) + O2(g) Calculate t

Basile [38]

Answer:

The enthalpy change for the given reaction is 424 kJ.

Explanation:

$2Cu(NO_3)_2(s)\rightarrow 2CuO(s) + 4NO_2(g) + O_2(g),\Delta H_{rxn}=?$

We have :

Enthalpy changes of formation of following s:

$\Delta H_{f,Cu(NO_3)_2}=-302.9 kJ/mol$

$\Delta H_{f,CuO}=-157.3 kJ/mol$

$\Delta H_{f,NO_2}= 33.2 kJ/mol$

$\Delta H_{f,O_2}= 0 kJ/mol$ (standard state)

$\Delta H_{rxn}=\sum [\Delta H_f(product)]-\sum [\Delta H_f(reactant)]$

The equation for the enthalpy change of the given reaction is:

$\Delta H_{rxn}$ =

$=(2 mol\times \Delta H_{f,CuO}+4\times \Delta H_{f,NO_2}+1 mol\times \Delta H_{f,O_2})-(2mol\times \Delta H_{f,Cu(NO_3)_2})$

$\Delta H_{rxn}$ =

$(2mol\times (-157.3 kJ/mol)+4\times 33.2 kJ/mol=1 mol\times 0 kJ/mol)-(2 mol\times (-302.9 kJ/mol)$

$\Delta H_{rxn}=424 kJ$

The enthalpy change for the given reaction is 424 kJ.

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2 years ago

The Safe Drinking Water Act (SDWA) sets a limit for mercury-a toxin to the central nervous system-at 0.002 mg/L. Water suppliers

posledela

Answer:

The volume of mercury-contaminated water that has to be consumed to ingest 0.100 g mercury is 2.50 × 10⁴ l

Explanation:

Hi there!

First, let´s convert 0.100 g to mg:

0.100 g · (1000 mg/1 g) = 100 mg

The contaminated water has 0.004 mg per liter, then, we have to find the volume of water that contains 100 mg of mercury:

100 mg · (1 l / 0.004 mg) = 2.50 × 10⁴ l

Then, the volume of mercury-contaminated water ( at a concentration of 0.004 mg/l) that has to be consumed to ingest 0.100 g mercury is 2.50 × 10⁴ l

Have a nice day!

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2 years ago

Two cars started at the same position and were driven through a city using different streets. The red car traveled north 2 miles

Bad White [126]

Answer:

C

green traveled les distance but still ended up in the same location as red

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2 years ago

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Recalling that a beaker of water is two dimensional, what is the three dimensional shape of the micelle

saul85 [17]

A micelle refers to an aggregate of a surfactant molecule, which a dispersed in a liquied colloid. In an aqueous liquid, a micelle is arranged in such a way that its hydrophillic head region will be in contact with the surrounding solvents while the hydrophobic tail region will be embedded in its center.
The three dimensional shape of a micelle is A SPHERE.

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2 years ago

A 5.024 mg sample of an unknown organic molecule containing carbon, hydrogen, and nitrogen only was burned and yielded 13.90 mg

Dafna1 [17]

Answer:

C8H17N

Explanation:

Mass of the unknown compound = 5.024 mg

Mass of CO2 = 13.90 mg

Mass of H2O = 6.048 mg

Next, we shall determine the mass of carbon, hydrogen and nitrogen present in the compound. This is illustrated below:

For carbon, C:

Molar mass of CO2 = 12 + (2x16) = 44g/mol

Mass of C = 12/44 x 13.90 = 3.791 mg

For hydrogen, H:

Molar mass of H2O = (2x1) + 16 = 18g/mol

Mass of H = 2/18 x 6.048 = 0.672 mg

For nitrogen, N:

Mass N = mass of unknown – (mass of C + mass of H)

Mass of N = 5.024 – (3.791 + 0.672)

Mass of N = 0.561 mg

Now, we can obtain the empirical formula for the compound as follow:

C = 3.791 mg

H = 0.672 mg

N = 0.561 mg

Divide each by their molar mass

C = 3.791 / 12 = 0.316

H = 0.672 / 1 = 0.672

N = 0.561 / 14 = 0.040

Divide by the smallest

C = 0.316 / 0.04 = 8

H = 0.672 / 0.04 = 17

N = 0.040 / 0.04 = 1

Therefore, the empirical formula for the compound is C8H17N

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2 years ago