The answer is 69.048%.

Mass of potassium dichromate (K₂Cr₂O₇) is 294 g, which is a 100%.

Given mass of chromium is 52 g. So, the mass percent of chromium in the compound is 17.687%:
52 g : x% = 294 g : 100%
x = 52 ÷ 294 × 100 %
x = 17.687%

Given mass of potassium is 39 g. So, the mass percent of potassium in the compound is 13.265%:
39 g : x% = 294 g : 100%
x = 39 ÷ 294 × 100 %
x = 13.265%

Therefore, the mass percent of oxygen in the compound is 69.048%:
100% - 17.687% - 13.265% = 69.048%.

5 0

4 years ago

Help please!!! My science homework is due in 2 days and I need help!

sertanlavr [38]

1) Because the crystals do not have much time to develop if the lava cools fast, they are quite tiny. If the lava cools gradually, the crystals will have ample time to form and become huge. The size of crystals in an igneous rock is a good predictor of the conditions under which the rock developed.

2) Intrusive igneous rocks cool slowly from magma in the crust. They have a lot of crystals. Extrusive igneous rocks cool fast from lava near the surface. They are covered with tiny crystals.

3) Usually they will contain metal elements that oxidise easily. For example, the Igneous rocks on them Moon (the Maria or 'oceans') are darker in colour due to a higher percentage of iron.

4) The hue of igneous rocks is proportional to their density. Darker colored rocks have a higher density because they contain more material and iron. Light colored rocks have a lesser density because they contain less material and iron.
5) Magma is hot, molten rock under the earth's surface; lava is when magma reaches the earth's surface (it is then called lava).
6) The mineral grains with a pegmatitic texture are unusually big. The biggest ones are often more than 3 cm long. In intrusive rocks, this texture can be seen. The fact that they were particularly big did not imply that they cooled slowly.
7) Igneous rocks are classified according to their origin, texture and mineral composition. A igneous rock formed from lava that erupted on to earths surface.

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ROR

5 0

2 years ago