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A 8.85 g sample of hydrate of sodium carbonate, Na,CO, XH,O was heated carefully until no more mass was lost from the sample After heating, the final weight of the material was 7.55 g What is the sodium carbonate (Na,cO,)-to-water mole ratio?
a) 1:0
b) 1:1
c) 2:1
d) 1:2

Answer :

Answer:

b) 1:1

Explanation:

Mass of the hydrated salt = 8.85 g

Mass of the dehydrated salt = 7.55 g

Mass of water lost = 8.85 - 7.55 g = 1.3 g

The moles of the dehydrated salt is :

Amount = 7.55 g

Molar mass of [tex]Na_2CO_3[/tex] = 105.9888 g/mol

The formula for the calculation of moles is shown below:

[tex]moles = \frac{Mass\ taken}{Molar\ mass}[/tex]

Thus, moles are:

[tex]moles= \frac{7.55\ g}{105.9888\ g/mol}[/tex]

[tex]moles= 0.07123\ mol[/tex]

The moles of water is :

Amount = 1.3 g

Molar mass of [tex]H_2O[/tex] = 18 g/mol

The formula for the calculation of moles is shown below:

[tex]moles = \frac{Mass\ taken}{Molar\ mass}[/tex]

Thus, moles are:

[tex]moles= \frac{1.3\ g}{18\ g/mol}[/tex]

[tex]moles= 0.0722\ mol[/tex]

The simplest ration of the two are:

[tex]Na_2CO_3:H_2O[/tex] = 0.07123 : 0.0722 = 1 : 1

Moles are the ratio of mass and molar mass of the solute in the substance or the compound. The ratio of sodium carbonate and water will be 1: 1.

What are moles?

Moles are the amount of the solute and are a measurement unit of the electrons, atoms and molecules. It can be given as the entity of the Avogadro number present.

Given,

  • Mass of the dehydrated salt = 7.55 g
  • Mass of the hydrated salt = 8.85 g
  • Mass of water lost = 1.3 g

Calculate the moles of the dehydrated salt:

[tex]\begin{aligned} \rm Moles &= \rm \dfrac {mass}{molar\; mass}\\\\&= \dfrac{7.55}{105.98}\\\\&= 0.0712\;\rm moles\end{aligned}[/tex]

Calculate the moles of the water:

[tex]\begin{aligned} \rm Moles &= \rm \dfrac {mass}{molar\; mass}\\\\&= \dfrac{1.3}{18}\\\\&= 0.0722\;\rm moles\end{aligned}[/tex]

Calculation of the ratio of the moles of salt and water is:

[tex]\begin{aligned} \rm Na_{2}CO_{3} : H_{2}O &= 0.0712: 0.0722\\\\&= 1: 1\end{aligned}[/tex]

Therefore, moles of salt and water are in the ratio of 1:1.

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