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3 years ago

The molar mass of element X is 42.3 grams per mol and the molar mass for

Chemistry

1 answer:

Drupady [299]3 years ago

7 0

Answer:

X5Y2

Explanation:

% composition of X = 52.2%

% composition of Y = (100 - 52.2) = 47.8%

This means that there are 52.2g of X and 47.8g of Y in the compound

To calculate the empirical formula of the compound, we first convert the gram value to mole value by dividing by their molar masses.

X = 52.2g/42.3g/mol = 1.234mol

Y = 47.8g/96.7g/mol = 0.494mol

Next, we divide each mole value by the smallest value (0.494mol)

X = 1.234mol ÷ 0.494mol = 2.49

Y = 0.494mol ÷ 0.494mol = 1

We multiply each value by 2

X = 2.49 × 2 = 4.98

Y = 1 × 2 = 2

The simple ratio of X:Y is 5:2, hence, their empirical formula is X5Y2.

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Which formula can be used to calculate the theoretical yield?

Bas_tet [7]

Answer:

Option C, (Actual yield ÷ percent yield) × 100

Explanation:

Theoretical yield is defined as the total amount of product formed for given reactants in a chemical reaction. It is an ideal case which assumes no exceptions or wastage.

The mathematical relation between the actual yield, percent yield and theoretical yield is as follows -

$P.Y. = \frac{M_{A.Y.}}{M_{T.Y.}} * 100$

Where

P.Y. represents the percent yield a

M A.Y. represents the mass obtained from actual yield

M T.Y. represents the mass obtained from theoretical yield

Hence, if we rearrange the formula, we get -

$M_{T.Y.} = \frac{M_{A.Y.}}{P.Y.} * 100$

Hence, option C is correct

5 0

3 years ago

A scientist digs up sample of arctic ice that is 458,000 years old. He takes it to his lab and finds that it contains 1.675 gram

Fiesta28 [93]

Answer:

6.70 grams of krypton-81 was present when the ice first formed

Explanation:

Let use the below formula to find the amount of sample

$N= N_0(\frac{1}{2})^n$

where

$n = \frac{t}{t_{\frac{1}{2}}}$

here

t = 458,000 years

$t_{\frac{1}{2}}$ = 229,000

$\frac{t}{t_{\frac{1}{2}}}$ = \ $\frac{ 458,000}{229,000}$

n = $\frac{t}{t_{\frac{1}{2}}}$ = 2.000

Now substituting the values

$1.675 = N_0(\frac{1}{2})^{2.000}}$

$1.675 = N_0\times (0.2500)$

$N_0= \frac{1.675}{0.2500}$

$N_0=6.70$

3 0

3 years ago

The molar mass is determined by measuring the freezing point depression of an aqueous solution. A freezing point of -5.20°C is r

Dima020 [189]

Answer:

The empirical formula is C2H4O3

The molecular formula is C4H8O6

The molar mass is 152 g/mol

Explanation:

The complete question is: An unknown compound contains only carbon, hydrogen, and oxygen. Combustion analysis of the compound gives mass percents of 31.57% C and 5.30% H. The molar mass is determined by measuring the freezing-point depression of an aqueous solution. A freezing point of -5.20°C is recorded for a solution made by dissolving 10.56 g of the compound in 25.0 g water. Determine the empirical formula, molar mass, and molecular formula of the compound. Assume that the compound is a nonelectrolyte.

Step 1: Data given

Mass % of Carbon = 31.57 %

Mass % of H = 5.30 %

Freezing point = -5.20 °C

10.56 grams of the compound dissolved in 25.0 grams of water

Kf water = 1.86 °C kg/mol

Step 2: Calculate moles of Carbon

Suppose 31.57% = 31.57 grams

moles C = mass C / Molar mass C

moles C = 31.57 grams / 12.0 g/mol = 2.63 moles

Step 3: Calculate moles of Hydrogen:

Moles H = 5.30 grams / 1.01 g/mol

moles H = 5.25 moles

Step 4: Calculate moles of Oxygen

Moles O = ( 100 - 31.57 - 5.30) / 16 g/mol

Moles O = 3.95 moles

Step 5: We divide by the smallest number of moles

C: 2.63 / 2.63 = 1 → 2

H: 5.25/2.63 = 2 → 4

O: 3.95/ 2.63 = 1.5 → 3

The empirical formula is C2H4O3

The molar mass of the empirical formula = 76 g/mol

Step 6: Calculate moles solute

Freezing point depression = 5.20 °C = m * 1.86

m = 5.20 / 1.86

m = 2.80 molal = 2.80 moles / kg

2.80 molal * 0.025 kg = 0.07 moles

Step 7: Calculate molar mass

Molar mass = mass / moles

Molar mass = 10.56 grams / 0.07 moles

Molar mass = 151 g/mol

Step 8: Calculate molecular formula

151 / 76 ≈ 2

We have to multiply the empirical formula by 2

2*(C2H4O3) = C4H8O6

The molecular formula is C4H8O6

The molar mass is 152 g/mol

6 0

4 years ago

If normal rainwater has a pH of about 6.50, what is the hydrogen ion concentration, [H+]?

IceJOKER [234]

Answer:

.000000316

Explanation:

H+=10^-pH

6 0

3 years ago

Can someone good with chemistry help me?

Digiron [165]

As you go down group 7 the melting point of the elements will increase, this is because as you go down the group you are gaining an electron shell and the molecule will become bigger. This increase in size means that there will be an increase in the intermolecular forces as well.

So the order would be NF3, NBr3, NI3.

Hopefully this helps!

6 0

3 years ago