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3 years ago

Question 2 how many valence electrons are in a neutral atom of silicon

Chemistry

1 answer:

marshall27 [118]3 years ago

7 0

Si -Atomic number -14 -1s2 2s2 2p6 3s2 3p2 - 4 valence electrons

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in which level of organization would the roots of a plant most likely be classified? Please explain too

abruzzese [7]

Kaka ml nyu yan wala kaming paki kung ano ang lagi ginagawa nyu

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3 years ago

I need help on 5,6,7. I would give you guys a thank you. This is going to be due very soon.

Ira Lisetskai [31]

Answer:

5) Plant; 6) Heat; 7) never heard of chemosynthesis, sorry :(

Explanation:

A plant is the only thing in an ecosystem that uses photosyenthesis. This includes trees, algea, and grass.

80% of energy is lost as heat used in order to keep the animal warm.

I am really sorry I couldn’t help with 7!

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3 years ago

I need help with the last two questions please help quickly!!

Talja [164]

Not sure about the last one, but I think the percent composition of zinc would be ~ 42.8232

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2 years ago

A stack of 10 pennies weighing 26.55 grams is placed in a graduated cylinder containing water. The initial volume of water is 50

BigorU [14]

In order to determine the density of an item, we will need to determine its mass and volume. The standard unit for measuring mass in a lab is the gram. Think about liquids- what units do you typically report the volume of a liquid in? What about for a sugar cube, what volume is the most appropriate?
A regular object like a sugar cube can be measured with a ruler so we might report the volume in centimeters cubed (cm3). An irregular object like the plate pictured below can be measured by using a technique called volume by displacement. A liquid (typically water) is placed in a graduated cylinder and the volume of a liquid is measured. Then the irregular object is placed in the liquid and the volume is measured again. The change in volume is the irregular object’s volume. This measurement is often made using a graduated cylinder and recording a volume in Liters or milliliters (mL).
Figure 1. (a) Regular object of metal blocks with the same width, length, and height. (B) An irregular

7 0

3 years ago

Ethanol, C2H6O, is most often blended with gasoline - usually as a 10 percent mix - to create a fuel called gasohol. Ethanol is

weeeeeb [17]

Answer:

This means 463 grams of ethanol would provide less amount of energy

Explanation:

Step 1: Data given

Heat of combustion of ethanol = 326.7 kcal/mol

The heat of combustion of octane = 1.308*10³ kcal/mol

Mass of octane = 463 grams

Molar mass octane = 114.23 g/mol

Molar mass ethanol = 46.07 g/mol

Step 2: Calculate moles octane

Moles octane = mass octane / molar mass octane

Moles octane = 463 grams / 114.23 g/mol

Moles octane = 4.05 moles

Step 3: Calculate energy of combustion of 4.05 moles octane

Combustion of 1 mol octane gives us: 1.308 * 10³ kcal/mol

Combustion of 4.05 moles octane gives us 4.05 * 1.308 * 10³ kcal/mol = 5.30 * 10³ kcal

This means the combustion reaction of 463 grams of octane gives us 5.30 * 10³ kcal

Step 4:

Heat of combustion of ethanol = 326.7 kcal/mol

OR in words: combustion of 1 mol ethanol gives us 326.7 kcal energy

Moles ethanol = 463 grams / 46.07 g/mol

Moles ethanol = 10.05 moles

Since combustion of 1 mol ethanol gives us 326.7 kcal

10.05 moles ethanol will give us = 10.05 * 326.7 = 3283.3 kcal = 3.28 * 10³ kcal

5.30 * 10³ kcal > 3.28 * 10³ kcal

This means 463 grams of ethanol would provide less amount of energy

3 0

3 years ago