Question

Calculate the mass of 2.25×1022 tungsten atoms. express the mass in grams to three significant figures

Answer 1

1 mole of an element = 6.02 x 10²³ atoms

That is 183.84 g of tungsten , contains 6.02 x 10²³ atoms

or 6.02 x 10²³ atoms=183.84 g of tungsten

6.02 x 10²³ atoms = 183.84 g

2.25 x 10²² atoms =

$(183.84\times \frac{2.25 \times 10^{22}}{6.02 \times 10 ^{23}}) g of tungsten$

                                                             g of tungsten  

                                     = 6.87 g  

So, the mass of 2.25×10²² tungsten atoms is 6.87 g  .

Answer 2

$\boxed{1.1255 \times {{10}^{23}}{\text{ atoms}}}$ of oxygen are present in 7.00 g of sodium dichromate.

Further Explanation:

Given information:

Number of tungsten atoms: $2.25 \times {10^{22}}{\text{ atoms}}$  

To calculate:

Mass of $2.25 \times {10^{22}}{\text{ atoms}}$ of tungsten

Steps to proceed:

Step I:Firstly moles of tungsten present in $2.25 \times {10^{22}}{\text{ atoms}}$ are to be calculated. This is done with the use of Avogadro’s law indicating that one mole of a substance is composed of $6.022 \times {10^{23}}{\text{ particles}}$. These particles can be atoms or molecules.

Since $6.022 \times {10^{23}}{\text{ atoms}}$ are present in one mole of tungsten, moles of tungsten present in of tungsten can be evaluated as follows:

$\begin{aligned}{\text{Number of tungsten atoms}} &= \left( {\frac{{1{\text{ mol}}}}{{6.022 \times {{10}^{23}}{\text{ atoms}}}}} \right)\left( {2.25 \times {{10}^{22}}{\text{ atoms}}} \right) \\&= 0.03736{\text{ mol}} \\\end{aligned}$  

Step II:Mass of 0.03736 moles of tungsten is to be calculated.

The formula to calculate moles of tungsten is as follows:

${\text{Moles of tungsten}} = \dfrac{{{\text{Mass of tungsten}}}}{{{\text{Molar mass of tungsten}}}}$                                              …… (1)

Rearrange equation (1) to calculate mass of tungsten.

${\text{Mass of tungsten}} = \left( {{\text{Moles of tungsten}}} \right)\left( {{\text{Molar mass of tungsten}}} \right)$             …… (2)

The value of moles of tungsten is 0.03736 mol.

The value of molar mass of tungsten is 183.84 g/mol.

Substitute these values in equation (2).

$\begin{aligned}{\text{Mass of tungsten}} &= \left( {{\text{0}}{\text{.03736 mol}}} \right)\left( {{\text{183}}{\text{.84 g/mol}}} \right) \\&= 6.87{\text{ g}} \\\end{aligned}$  

Learn more:

1. How many moles of Cl are present in 8 moles of ${\text{CC}}{{\text{l}}_4}$ ? https://brainly.com/question/3064603
2. Calculate the moles of ions in HCl solution: https://brainly.com/question/5950133

Answer details:

Grade: Senior School

Subject: Chemistry

Chapter: Mole concept

Keywords: tungsten, moles, mass, molar mass, 6.87 g, 0.03736 mol, 183.84 g/mol, moles of tungsten, tungsten, 2.25*10^22 atoms, Avogadro’s law, 6.022*10^23 atoms, one mole, atoms, molecules.