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3 years ago

Which evidence is an indication that a chemical reaction has occurred?

Chemistry

1 answer:

Luden [163]3 years ago

8 0

Answer:

Some signs of a chemical change are a change in color and the formation of bubbles. The five conditions of chemical change: color change, formation of a precipitate, formation of a gas, odor change, temperature change.

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Which of these expressions are correct variations of the Combined Gas Law?

mafiozo [28]

Answer:

Both

Explanation:

The combined gas law is also known as the general gas law.

From the ideal gas law we assume that n = 1;

So;

PV = nRT

and then;

$\frac{P_{1}V_{1} }{T_{1} }$ = $\frac{P_{2}V_{2} }{T_{2} }$

If we cross multiply;

P₁V₁T₂ = P₂V₂T₁

So;

T₁ = $T_{2} \frac{P_{1}V_{1} }{P_{2} V_{2} }$

Also;

V₂ = $V_{1} \frac{P_{1} T_{2} }{P_{2} T_{1} }$

So from the choices both are correct

3 0

3 years ago

Which of the following choices would have a positive entropy change?

aalyn [17]

Answer:

The option B) Fe₂O₃ (s) + 3C(s) → 2Fe(s) + 3CO₂(g), because the reactants are only solid units and the products contain gas molecules.

Explanation:

A positive entropy change means that the entropy of the products is greater than the entropy of the reactants.

Entropy in a measure of the radomness or disorder of the system.

Let's see every reaction:

A) 4NO₂ (g) + 2 H₂O (l) + O₂ (g) → 4 HNO₃ (aq)

Since 5 molecules of a gas (high disorder) combines with 2 molecules of liquid to produce 4 units of aqueous HNO₃ you may expect that the product is more ordered than the reactants, which means that the change in entropy is negative (the entropy decreases).

B) Fe₂O₃ (s) + 3C(s) → 2Fe(s) + 3CO₂(g)

The left side (reactants) show only solid substances which is a highly ordered arrangement while the right side (products) show the formation a solid (ordered arrangement) and a gas (highly disoredered arrangement), so you can predict the increase of the system entropy, i.e. a positive entropy change.

The equation C) shows the combination of 12 gas molecules to produce 1 solid and 6 gas molecules, so you can expect that the entropy will decrease, i.e. a negative entropy change.

For equation D) the products include solid and gas reactants while the product is just one unit of solid substance, letting you to predict a negative entropy change.

4 0

3 years ago

What is meant by Orion? for grade 10

wariber [46]

Answer:

[Latin (genitive Orionis)] : a constellation on the equator east of Taurus represented on charts by the figure of a hunter with belt and sword. 2 : a giant hunter slain by Artemis in Greek mythology.

Explanation:

8 0

3 years ago

Read 2 more answers

How would you compare Uranus (a Jovian planet) to Earth (a terrestrial planet)?

kipiarov [429]

Answer:
Uranus is much bigger than Earth.
Explanation:
it’s about four times bigger than the watch, Uranus is about 31,000 miles in diameter while the earth is only about 7,900 miles.

3 0

3 years ago

The tungsten- nuclide radioactively decays by alpha emission. Write a balanced nuclear chemical equation that describes this pro

Scrat [10]

Answer:

The solution to this question can be defined as follows:

Explanation:

The complete question is defined in the attached file.

$W^{180}_{74} \to He^{4}_{2} + Hf^{176}_{72}$