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3 years ago

How do I identify significant figures in chemistry?

1 answer:

3 0

1) START counting for sig. figs. On the FIRST non-zero digit.

2) STOP counting for sig. figs. On the LAST non-zero digit.

3) Non-zero digits are ALWAYS significant.

4) Zeroes in between two non-zero digits are significant. All other zeroes are insignificant.

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Phosphorous pentoxide, P2O5(s), is produced from the reaction between pure oxygen and pure phosphorous (P, solid). What is the v

BartSMP [9]

Answer:

4190.22 L = 4.19 m³.

Explanation:

For the balanced reaction:

2P₂ + 5O₂ ⇄ 2P₂O₅.

It is clear that 2 mol of P₂ react with 5 mol of O₂ to produce 2 mol of P₂O₅.

Firstly, we need to calculate the no. of moles of 6.92 kilograms of P₂O₅ produced through the reaction:

no. of moles of P₂O₅ = mass/molar mass = (6920 g)/(283.88 g/mol) = 24.38 mol.

Now, we can find the no. of moles of O₂ is needed to produce the proposed amount of P₂O₅:

Using cross multiplication:

5 mol of O₂ is needed to produce → 2 mol of P₂O₅, from stichiometry.

??? mol of O₂ is needed to produce → 24.38 mol of P₂O₅.

∴ The no. of moles of O₂ needed = (5 mol)(24.38 mol)/(2 mol) = 60.95 mol.

Finally, we can get the volume of oxygen using the general law of ideal gas: PV = nRT.

where, P is the pressure of the gas in atm (P = 606.1 mm Hg/760 = 0.8 atm).

V is the volume of the gas in L (V = ??? L).

n is the no. of moles of the gas in mol (n = 60.95 mol).

R is the general gas constant (R = 0.0821 L.atm/mol.K),

T is the temperature of the gas in K (396.90°C + 273 = 669.9 K).

∴ V of oxygen needed = nRT/P = (60.95 mol)(0.0821 L.atm/mol.K)(669.9 K)/(0.8 atm) = 4190.22 L/1000 = 4.19 m³.

3 0

3 years ago

How can you tell the number of covalent bonds an element can form?

Sergio039 [100]

The number of bonds for a neutral atom is equal to the number of electrons in the full valence shell (2 or 8 electrons) minus the number of valence electrons. This method works because each covalent bond that an atom forms adds another electron to an atoms valence shell without changing its charge.

3 0

3 years ago

What is the energy of an electromagnetic wave with a frequency of 8 x 10^12

omeli [17]

Answer:

Energy, $E=5.3\times 10^{-21}\ J$

Explanation:

It is required to find the energy of an electromagnetic wave with a frequency of $8\times 10^{12}\ Hz$ . The energy of a wave in terms of its frequency is given by :

$E=h\nu$

$\nu$ = frequency of em wave

$E=6.63\times 10^{-34}\times 8\times 10^{12}\\\\E=5.3\times 10^{-21}\ J$

So, the energy of an electromagnetic wave is $5.3\times 10^{-21}\ J$

4 0

3 years ago

CORO Name three ways that scientists can ensure their results are reliable

Leya [2.2K]

Answer:

Reliability. When a scientist repeats an experiment with a different group of people or a different batch of the same chemicals and gets very similar results then those results are said to be reliable. Reliability is measured by a percentage – if you get exactly the same results every time then they are 100% reliable.

Explanation:

Sorry, I only got one way.

5 0

3 years ago

If you are given a 0. 31 g piece of sodium metal to react with water, how many moles of hcl would it take to neutralize the sodi

Sphinxa [80]

The moles of HCl to neutralize the sodium hydroxide produced is 0.0135 mole.

Neutralization or neutralization is a chemical response wherein an acid and a base react quantitatively with each other. In a reaction in water, neutralization outcomes in there being no excess of hydrogen or hydroxide ions gift in the answer.

calculation:-

2Na + 2H₂O -----> 2NaOH + H₂

2 mol or 46g of Na produces 80 grams of NaOH

∴ 0.31 g of Na will produce = 80/46 × 0.31

= 0.54 gram of NaOH.

mol of NaOH = 0.54/40

= 0.0135

Since both Hcl and NaOH have the same valance factor,

1 mole NaOH is needed to neutralize 1 mol HCl

∴ 0.0135 mole of NaOH will need = 0.0135 mole of HCl

mass = 0.0135 × 36.5

= 0.493 grams of HCL.

Learn more about neutralizing here:-brainly.com/question/23008798

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4 0

1 year ago