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3 years ago

True or false the si in sih4 does not follow the octet rule because hydrogen is in an unusual oxidation stat

1 answer:

6 0

The statement is true. The octet rule refers to the general rule of thumb wherein atoms of main-group elements tend to bond with other atoms in such a way that each atom possesses eight electrons (octet) in their valence shell. They tend to form the same electronic configuration as the noble gases. However, there are some exceptions to this rule. One of which is silane, SiH₄. A hydrogen atom only has 1 valence electron and needs another electron to complete its energy level. This is unlike other atoms, for example, carbon which has 4 valence electrons and needs to form 4 covalent bonds to fill its energy levels. Thus, 4 hydrogen atoms need only 4 more electrons. This is given by the silicon atom which has 4 valence electrons. Therefore, when a silicon atom is bonded to 4 hydrogen atoms, the resulting molecule, SiH₄, is a stable one.

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A mixture consists of sand and an aqueous salt

Alenkinab [10]

Answer is (4).

Explanation:

The given mixture contains an insoluble solid and an aqueous solution of salt. The insoluble solid is sand. 

First we have to separate insoluble solid. Sand can be separated by doing filtration. When we filter the mixture sand can be seen as the residue on the filter paper.

After filtering the mixture, we should collect the filtrate. Filtrate is the salt solution. By doing evaporation we can get the solid salt. 

First and second choices are wrong because after evaporating water filtration cannot be done and salt and sand will be mixed together.

Salt cannot be filtered out because the salt is soluble and it is in aqueous medium. Hence, third choice is wrong

7 0

3 years ago

Read 2 more answers

What are moles in chemistry?

Firlakuza [10]

A mole is a unit to describe an amount of something/specific substance. Typically standard for measuring a large quantity of small entities like atoms, molecules, or other particles.

3 0

3 years ago

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How many kilojoules of energy would be required to heat a 225g block of aluminum from 23.0 C to 73.5 C?

gulaghasi [49]

Answer:

$\boxed {\boxed {\sf 10.2 \ kJ}}$

Explanation:

We are asked to find how many kilojoules of energy would be required to heat a block of aluminum.

We will use the following formula to calculate heat energy.

$q=mc \Delta T$

The mass (m) of the aluminum block is 225 grams and the specific heat (c) is 0.897 Joules per gram degree Celsius. The change in temperature (ΔT) is the difference between the final temperature and the initial temperature.

ΔT = final temperature - inital temperature

The aluminum block was heated from 23.0 °C to 73.5 °C.

ΔT= 73.5 °C - 23.0 °C = 50.5 °C

Now we know all three variables and can substitute them into the formula.

m= 225 g
c= 0.897 J/g° C
ΔT= 50.5 °C

$q= (225 \ g )(0.897 \ J/g \textdegree C)(50.5 \textdegree C)$

Multiply the first two numbers. The units of grams cancel.

$q= (225 \ g * 0.897 \ J/g \textdegree C)(50.5 \textdegree C)$

$q= (225 * 0.897 \ J / \textdegree C)(50.5 \textdegree C)$

$q= (201.825\ J / \textdegree C)(50.5 \textdegree C)$

Multiply again. This time, the units of degrees Celsius cancel.

$q= 201.825 \ J * 50.5$

$q= 10192.1625 \ J$

The answer asks for the energy in kilojoules, so we must convert our answer. Remember that 1 kilojoule contains 1000 joules.

$\frac { 1 \ kJ}{ 1000 \ J}$

Multiply by the answer we found in Joules.

$10192.1625 \ J * \frac{ 1 \ kJ}{ 1000 \ J}$

$10192.1625 * \frac{ 1 \ kJ}{ 1000 }$

$\frac {10192. 1625}{1000} \ kJ$

$10.1921625 \ kJ$

The original values of mass, temperature, and specific heat all have 3 significant figures, so our answer must have the same. For the number we found, that is the tneths place. The 9 in the hundredth place tells us to round the 1 up to a 2.

$10.2 \ kJ$

Approximately 10.2 kilojoules of energy would be required.

3 0

3 years ago

Can you use active transport in a sentence

otez555 [7]

Active transport is the moving of molecules across the membrane of the cell against the concentration gradient with the use of ATP.

Low to high concentration. Concentration gradient is the diffusion (movement of molecules from regions of low concentration) from high to low with the gradient. Active transport is from low to high, against the gradient.

6 0

4 years ago

Read 2 more answers

Classifying Chemical Reactions

olga2289 [7]

Answer:

chemestry

Explanation:

5 0

3 years ago