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3 years ago

A sample of V weighs 61.9 grams. Will a sample of He that contains the same number of atoms weigh more or less than 61.9 grams

Chemistry

1 answer:

damaskus [11]3 years ago

6 0

Answer:

Weigh less than 61.9 g

Explanation:

The symbol V represents the element Vanadium and He represents Helium.

Generally, 1 mol of any atom contains 6.022 * 10^23 atoms. This means we have to find the number of moles of each elements.

For V;

Number of moles = Mass / Molar mass = 61.9 / 50.94 = 1.215 mol

1 mol = 6.022 * 10^23 atoms

1.215 = x

Number of atoms = 6.022 * 10^23 * 1.215 =7.317 * 10^23

For He;

Since equal number of moles contain equal number of atoms;

Number of mol of He = 1.215 mol

Number of moles = Mass / Molar mass

Mass = Molar mass * Number of moles = 4 * 1.215 = 4.86 g

This means it would weigh less.

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A solution was prepared by mixing 0.5000 m hno2 with 0.380 m no2-. ka = 4.58 x 10-4. calculate the ph of the solution. show work

adell [148]

pH of buffer can be calculated as:

pH=pKa+log[salt]/[Acid]

As ka = 4.58 x 10-4

Concentration of [Salt] that is NO2(-1)=0.380M

Concentration of [Acid] that is HNO2=0.500M

So, pH= -log(4.58*10^-4)+log((0.380)/0.500))

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Explanation:

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3 years ago

17)<br> How many grams are in 0.02 moles of beryllium iodide, Bel2?

Alinara [238K]

Answer:

beryllium iodide has a molar mass of 262.821 g mol−1 , which means that 1 mole of beryllium iodide has a mass of 262.821 g . To find the mass of 0.02 moles of beryllium iodide, simply multiply the number of moles by the molar mass in conversion factor form.

Explanation:

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3 years ago

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: Citric acid, H3C6H5O7, is a triprotic acid. Consider a buffer system comprising H2C6H5O7 - and HC6H5O7 2- ions. What is the ne

olchik [2.2K]

Answer:

The Net reaction is

$H_3C_6H_5O_7 + 0H^- ----> H_2C_6H_5O_7^- +H_2O \ \ \ \ \ \ \ Main \ Reaction$
$H_2C_6H_5O_7^ - + OH^- ----> H_C_6H_5O_7^{ 2-} + H_2O \ \ \ \ Add \ NaOH$
$HC_6H_5O_7 ^{2-} + OH^- ---> C_6H_5O_7^{3-} +H_2O \ \ \ \ \ Add \ NaOH$

Explanation:

From the Question we are told that the buffers are

$H_2C_6H_5O_7^ -$ and $HC_6H_5O_7 ^{ 2-}$

When NaOH is added the Net ionic reaction would be

$H_3C_6H_5O_7 + 0H^- ----> H_2C_6H_5O_7^- +H_2O \ \ \ \ \ \ \ Main \ Reaction$
$H_2C_6H_5O_7^ - + OH^- ----> H_C_6H_5O_7^{ 2-} + H_2O \ \ \ \ Add \ NaOH$
$HC_6H_5O_7 ^{2-} + OH^- ---> C_6H_5O_7^{3-} +H_2O \ \ \ \ \ Add \ NaOH$

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Suppose of copper(II) acetate is dissolved in of a aqueous solution of sodium chromate. Calculate the final molarity of acetate

uranmaximum [27]

Answer:

0.0714 M for the given variables

Explanation:

The question is missing some data, but one of the original questions regarding this problem provides the following data:

Mass of copper(II) acetate: $m_{(AcO)_2Cu} = 0.972 g$

Volume of the sodium chromate solution: $V_{Na_2CrO_4} = 150.0 mL$

Molarity of the sodium chromate solution: $c_{Na_2CrO_4} = 0.0400 M$

Now, when copper(II) acetate reacts with sodium chromate, an insoluble copper(II) chromate is formed:

$(CH_3COO)_2Cu (aq) + Na_2CrO_4 (aq)\rightarrow 2 CH_3COONa (aq) + CuCrO_4 (s)$

Find moles of each reactant. or copper(II) acetate, divide its mass by the molar mass:

$n_{(AcO)_2Cu} = \frac{0.972 g}{181.63 g/mol} = 0.0053515 mol$

Moles of the sodium chromate solution would be found by multiplying its volume by molarity:

$n_{Na_2CrO_4} = 0.0400 M\cdot 0.1500 L = 0.00600 mol$

Find the limiting reactant. Notice that stoichiometry of this reaction is 1 : 1, so we can compare moles directly. Moles of copper(II) acetate are lower than moles of sodium chromate, so copper(II) acetate is our limiting reactant.

Write the net ionic equation for this reaction:

$Cu^{2+} (aq) + CrO_4^{2-} (aq)\rightarrow CuCrO_4 (s)$

Notice that acetate is the ion spectator. This means it doesn't react, its moles throughout reaction stay the same. We started with:

$n_{(AcO)_2Cu} = 0.0053515 mol$

According to stoichiometry, 1 unit of copper(II) acetate has 2 units of acetate, so moles of acetate are equal to:

$n_{AcO^-} = 2\cdot 0.0053515 mol = 0.010703 mol$

The total volume of this solution doesn't change, so dividing moles of acetate by this volume will yield the molarity of acetate:

$c_{AcO^-} = \frac{0.010703 mol}{0.1500 L} = 0.0714 M$

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4 years ago