Assume that 12.0 g of oxygen are reacted with 20.0 g of magnesium to produce magnesium oxide.

1 answer:

8 0

Write out the eqn of magnesium and oxygen. this should be under “metals” chapter. do revise.

next, find the mols of both oxygen and magnesium. compare the ratios and find the LIMITING REAGENT.

use the mols of the limiting reagent to compare with the mols of the product.

take the mols of the product/mr of the product.

this will give u the mass.

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What is the definition of the molar mass of an element or compound?

VashaNatasha [74]

Answer:

The molar mass is the mass of a given chemical element or chemical compound (g) divided by the amount of substance(mol) .

Explanation:

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2 years ago

Calculate the freezing point of a solution containing 5.0 grams of KCl and 550.0 grams of water. The molal-freezing-point-depres

yulyashka [42]

<u>Answer:</u> The freezing point of solution is -0.454°C

<u>Explanation:</u>

Depression in freezing point is defined as the difference in the freezing point of pure solution and freezing point of solution.

The equation used to calculate depression in freezing point follows:

$\Delta T_f=\text{Freezing point of pure solution}-\text{Freezing point of solution}$

To calculate the depression in freezing point, we use the equation:

$\Delta T_f=iK_fm$

Or,

$\text{Freezing point of pure solution}-\text{Freezing point of solution}=i\times K_f\times \frac{m_{solute}\times 1000}{M_{solute}\times W_{solvent}\text{ (in grams)}}$

where,

Freezing point of pure solution = 0°C

i = Vant hoff factor = 2

$K_f$ = molal freezing point elevation constant = 1.86°C/m

$m_{solute}$ = Given mass of solute (KCl) = 5.0 g

$M_{solute}$ = Molar mass of solute (KCl) = 74.55 g/mol

$W_{solvent}$ = Mass of solvent (water) = 550.0 g

Putting values in above equation, we get:

$0-\text{Freezing point of solution}=2\times 1.86^oC/m\times \frac{5\times 1000}{74.55g/mol\times 550}\\\\\text{Freezing point of solution}=-0.454^oC$