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2 years ago

Is quartz(SiO2) a substance or mixture?

Chemistry

1 answer:

Illusion [34]2 years ago

8 0

Quartz is a substance because the material has uniform properties throughout and is held together via chemical bonds.

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What is the result of the following calculation? Record to the correct number of significant figures.

andriy [413]

Answer:

8.15103

Explanation:

3 0

2 years ago

If a 65 kilogram student exerts a force with a magnitude of 100 N on a 100 kilogram desk the magnitude of the force that the des

mrs_skeptik [129]

C. The action/reaction law states that a force is equal in both directions.

4 0

3 years ago

Analysis of an unknown substance indicates that it is a brittle solid. It acts as an electrical insulator (does not conduct) as

Musya8 [376]

Answer:

KBr

Explanation:

A metal has a very high melting point. Aluminum is a metal.

Ionic solids do not conduct electricity in the solid state. However, when the solids are melted, they conduct electricity.

KBr is an ionic substance, it can only conduct electricity in molten form because the ions are locked up in the solid.

5 0

2 years ago

In a sample of UO 2, the uranium has been enriched so that 3.0% of it is 235U. How long could the fissioning of the uranium in t

8090 [49]

Explanation:

Molecular mass of $UO_{2}$ is the sum of molecular mass of U and $O_{2}$ molecule.

Molar mass of $UO_{2}$ = (238 + 32) g/mol

= 270 g/mol

Hence, in 1 kg there are 1000 grams. So, total number of atoms given molecules present in 1 kg will be calculated as follows.

$\frac{1000 g}{270 g/mol} \times 6.023 \times 10^{23}atoms$

= $2.229 \times 10^{24}$

Hence, number of $^{235}U$ = $\frac{3}{100} \times 2.229 \times 10^{24}$

= $6.69 \times 10^{22}$

Now, let x seconds is required for burning 100 W lamp bulb. As 200 MeV is released per reaction.

100 x = $6.69 \times 10^{22} \times 200 \times 10^{6} \times 1.6 \times 10^{-19}$

x = $21.4 \times 10^{9}$ sec

Converting this value of x into years as follows.

x = $\frac{21.4 \times 10^{9}}{3600 \times 24 \times 365}$

x = $6.8 \times 10^{2}$ years

Thus, we can conclude that fissioning of the uranium in given situation requires $6.8 \times 10^{2}$ years to keep a 100 W lamp burning.

6 0

2 years ago

Which project provided evidence for the accelerated expansion of the universe?

ludmilkaskok [199]

The universe includes galaxies, the solar system, and planets. The accelerated expansion of the universe was provided by the Supernova Cosmology Project and High-Z Supernova Search Team. Thus, option B is correct.

<h3>What is Supernova Cosmology Project?</h3>

The Supernova Cosmology project in 1998, was to show the acceleration of the Universe's expansion. This project studied the acceleration rate of the universe that was expanding at a constant rate.

The Viking and Voyager missions were the first successful landing of spacecraft on the moon's surface. That didn't provide any information on the universe.

Therefore, option B. Supernova Cosmology Project provided evidence of the expansion.

Learn more about Supernova Cosmology Project here:

brainly.com/question/12534160

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7 0

1 year ago