All categories

2 years ago

If 20.0g of MgSO4⋅7H2O is thoroughly heated, what mass of anhydrous magnesium sulfate will remain?

2 answers:

7 0

We know that :
<span>MgSO4.7H2O + heat = MgSO4 + 7 H2O
</span>Also,
molar mass of MgSO4*7H2O = 246.47 g/mole
molar mass of MgSO4(anhydrous) = 120.415 g/mole

Therefore,
<span>Remaining mass of anhydrous magnesium sulfate = </span>(20 grams of MgSO4⋅7H2O) / (246.4746 grams of MgSO4⋅7H2O/mole) x (1 mole of MgSO4 / 1 mole of MgSO4⋅7H2O) x (120.3676 grams of MgSO4/mole )
= 7.7 grams of MgSO4

alina1380 [7]2 years ago

5 0

Answer: 9.8g

Explanation:

The calculation is based on the fact that all the water in the molecule will be removed.

i will, then, calculate the mass of water removed and then subtract it from the original 20.0 g of sample.

You can do that following these steps.

1) Calculate the number of moles of the hydrated magnsium sulfate, MgSO₄⋅7H₂O

number of moles = mass in grams / molar mass

The molar mass of MgSO₄⋅7H₂O is calcualted from the atomic mass of each atom times the number of atoms in the formula:

molar mass = 24.305 g/mol + 32.065 g/mol + 4×15.999g/mol + 7×2×1.008g/mol + 7×15.999 g/mol = 246.471 g/mol

⇒ moles of MgSO₄⋅7H₂O = 20.0g / 246.471 g/mol = 0.0811 moles

2) Calculate the number of moles of water, using the ratio from the chemical formula:

7 moles H₂O / 1 mol MgSO₄⋅7H₂O = x / 0.0811 mols MgSO₄⋅7H₂O

⇒ x = 0.0811 × 7 moles H₂O = 0.568 moles H₂O

3) Convert moles of H₂O to grams:

number of moles = mass in grams × molar mass = 0.568 moles × 18.015 g/mol = 10.2 g

4) Hence the mass remaining is 20.0g - 10.2g = 9.8g

You might be interested in

Twenty-seven milliliters of an acid with an unknown concentration are titrated with a base that has a concentration of 0.55 M. T

Svetllana [295]

It should be 0.25 M. Use the formula C1*V1=C2*V2, for those values, as it is right when it changed colour. Remember to change the if those are not the same (but in your case it is, so no need this time).

C1*V1=C2*V2
C1*27ml=0.55M*12.5ml
C1=(0.55M*12.5ml)/27ml = 0.25M

4 0

2 years ago

Read 2 more answers

In the synthesis of barium carbonate from an alkali metal carbonate (M2CO3 where M is one of the alkali metals) a student genera

Paraphin [41]

Answer:

0.019 moles of M2CO3

Explanation:

M2CO3(aq) + BaCl2 (aq) --> 2MCl (aq) + BaCO3(s)

From the equation above;

1 mol of M2CO3 reacts to produce 1 mol of BaCO3

Mass of BaCO3 formed = 3.7g

Molar mass of BaCO3 = 197.34g/mol

Number of moles = Mass / Molar mass = 3.7 / 197.34 = 0.0187 ≈ 0.019mol

Since 1 mol of M2CO3 reacts with 1 mol of BaCO3,

1 = 1

x = 0.019

x = 0.019 moles of M2CO3

3 0

2 years ago

Percentage yield of sodium peroxide if 5 g of sodium oxide produces 5.5 g of sodium peroxide

Rama09 [41]

<h3>Answer:</h3>

87.40 %

<h3>Explanation:</h3>

Concept being tested: Percent yield of a product

We are given;

Mass of Sodium oxide 5 g

Experimental or Actual yield of sodium peroxide IS 5.5 g

We are required to calculate the percent yield of sodium peroxide;

The equation for the reaction that forms sodium peroxide is

2Na₂O + O₂ → 2Na₂O₂

<h3>Step 1; moles of sodium oxide</h3>

Moles = mass ÷ molar mass

Molar mass of sodium oxide is 61.98 g/mol

Therefore;

Moles = 5 g ÷ 61.98 g/mol

= 0.0807 moles

<h3>Step 2: Theoretical moles of sodium peroxide produced </h3>

From the equation, 2 moles of sodium oxide produces 1 mole of sodium peroxide.

Thus, moles of sodium peroxide used is 0.0807 moles

<h3>Step 3: Theoretical mass of sodium peroxide used</h3>

Mass = Number of moles × Molar mass

Molar mass of sodium peroxide = 77.98 g/mol

Therefore;

Theoretical mass = 0.0807 moles × 77.98 g/mol

= 6.293 g

Theoretical mass of Na₂O₂ is 6.293 g

<h3>Step 4: Percent yield of Na₂O₂</h3>

We know that percent yield is given by the ratio of actual yield to theoretical yield expressed as a percentage.

$Percent yield=(\frac{Actual yield}{theoretical yield})100$

$Percent yield(Na_{2}O_{2})=(\frac{5.5g}{6.293g})100$

= 87.40 %

Therefore, the percentage yield of sodium peroxide is 87.4%

8 0

2 years ago

The pKs of succinic acid are 4.21 and 5.64. How many grams of monosodium succinate (FW = 140 g/mol) and disodium succinate (FW =

Varvara68 [4.7K]

Answer:

9.744g of monosodium succinate.

4.925g of disodium succinate.

Explanation:

To find pH of the buffer produced by the mixture of monosodium succinate-Disodium succinate is obtained from H-H equation:

pH = pKa + log ([Na₂Suc] / [NaHSuc])

As you want a pH of 5.28 and pKa is 5.64:

5.28 = 5.64 + log ([Na₂Suc] / [NaHSuc])

-0.36 = log ([Na₂Suc] / [NaHSuc])

0.4365 = ([Na₂Suc] / [NaHSuc]) <em>(1)</em>

<em />

As total concentration of the buffer is 100mM = 0.100M:

0.100M = [Na₂Suc] + [NaHSuc] <em>(2)</em>

Replacing (2) in (1):

0.4365 = (0.100M - [NaHSuc] / [NaHSuc])

0.4365 [NaHSuc] = 0.100M - [NaHSuc]

1.4365 [NaHSuc] = 0.100M

[NaHSuc] = 0.0696M

And:

[Na₂Suc] = 0.0304M

As volume of the buffer is 1L:

[NaHSuc] = 0.0696 moles

[Na₂Suc] = 0.0304 moles

Using molar mass of both substances:

Mass of monosodium succinate:

0.0696moles * (140g / 1mol) =<em> 9.744g of monosodium succinate.</em>

Mass of disodium succinate:

0.0304moles * (162g / 1mol) =<em> 4.925g of disodium succinate.</em>

5 0

2 years ago

The interior of a refrigerator has a volume of 0.600 m3. the temperature inside the refrigerator in 282 k, and the pressure is 1

Dafna11 [192]

In this instance we can use the ideal gas law equation to find the number of moles of gas inside the refrigerator
PV = nRT
where
P - pressure - 101 000 Pa
V - volume - 0.600 m³
n - number of moles
R - universal gas constant - 8.314 J/mol.K
T - temperature - 282 K
substituting these values in the equation
101 000 Pa x 0.600 m³ = n x 8.314 J/mol.K x 282 K
n = 25.8 mol
there are 25.8 mol of the gas
to find the mass of gas
mass of gas = number of moles x molar mass of gas
mass = 25.8 mol x 29 g/mol = 748.2 g
mass of gas present is 748.2 g

6 0

2 years ago