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3 years ago

List four observation that suggest a chemical change is occuring

Chemistry

1 answer:

andrezito [222]3 years ago

8 0

1.) Gas given off
2.) precipitate formed
3.) large amount of heat given off
4.) Color change

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How many moles of methanol must be added to 4.50 kg of water to lower its freezing point to -11.0 ∘c? for each mole of solute, t

DochEvi [55]

Given:

Mass of solvent water = 4.50 kg

Freezing point of the solution = -11 C

Freezing point depression constant = 1.86 C/m

To determine:

Moles of methanol to be added

Explanation:

The freezing point depression ΔTf is related to the molality m through the constant kf, as follows:

ΔTf = kf*m

where ΔTf = Freezing point of pure solvent (water) - Freezing pt of solution

ΔTf = 0 C - (-11.0 C) = 11.0 C

m = molality = moles of methanol/kg of water = moles of methanol/4.50 kg

11.0 = 1.86 * moles of methanol/4.50

moles of methanol = 26.613 moles

Ans: Thus around 26.6 moles of methanol should be added to 4.50 kg of water.

3 0

3 years ago

¿Cuál es la cantidad de electrones (e-) de Níquel si tiene una masa atómica de 58.6 y un número

daser333 [38]

Answer:

Hi do we translate a this

Explanation:

4 0

2 years ago

Balance the chemical equation: KOH + H3AsO4 → K2HAsO4 + H2O

Colt1911 [192]

2 KOH +1 H3AsO4 →1 K2HAsO4 + 2 H2O

3 0

3 years ago

Sam believes the rock is more denser than the pencil. He measured the mass of the rock to be 8.5 grams and volume to be 4.5mL. H

mezya [45]

Answer:

Rock

Explanation:

Let's calculate the density of each object:

Rock:

$Density = \frac{mass}{volume}=\frac{8.5\ g}{4.5\ mL}=1.9\ g/mL$

Pencil:

$Density = \frac{mass}{volume}=\frac{2.4\ g}{4.5\ mL}=0.53\ g/mL$

Therefore the rock is denser.

6 0

2 years ago

What is the number of the group that has the most reactive nonmetals (give number and letter- Ex 1A, 2A, etc.)?

Kryger [21]

Answer:

Group 7A

Explanation:

The group 7A elements consists of the most reactive non-metals on the periodic table.

This group is known as the group of halogens. They consist of element fluorine, chlorine, bromine, iodine and astatine.

The elements in this group have the highest electronegativity values.
They have 7 valence electrons and requires just one electron to complete their octets.
This way, they are highly reactive in their search for that single electron.

3 0

3 years ago