# 1.1 Moles and Molar Mass

ID: kojis-varig
Espy, BP BY-NC
Subject: Chemistry

This Grade 10-12, AP assignment contains 12 questions where students focus on Moles and Molar Mass. These exercises provide practice for Atomic Structures and Properties. For calculations in this assignment, molar masses for elements are taken from ptable.com. Avogadro's number is used with 3 significant figures in calculations. All answers are rounded to the appropriate number of significant figures.

12 questions

# 1.1 Moles and Molar Mass

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##### Formula to Molar Mass

1) Determine the molar mass of ﻿$(NH_{4})_{2}SO_{4}$﻿ in ﻿$\frac{g}{mol}$﻿.

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2) ﻿$1\text{ gram }$﻿samples of each of the following substances are measured. Which sample will contain the largest number of molecules?

a)

﻿$H_{3}O^{+1}$﻿

b)

﻿$C_{2}O^{2-}_{4}$﻿

c)

﻿$NH^{+1}_{4}$﻿

d)

﻿$NO^{-1}_{3}$﻿

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3) Determine the molar mass ﻿$\left(\frac{g}{mol}\right)$﻿ of the ionic compound consisting of ﻿$Al^{3+}\text{ and }SO_4^{2-}$﻿.

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For the following, assume ﻿$1\text{ mol}=6.02\times10^{23}$﻿ representative particles.

4) How many formula units are present in a ﻿$2.00\text{ gram }$﻿sample of ﻿$NaCH_3COO$﻿?

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5) What is the mass ﻿$(g)$﻿of ﻿$2.21\times10^{12}$﻿molecules of glucose, ﻿$C_6H_{12}O_6$﻿?

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6) How many molecules are present in a ﻿$0.00250$﻿ gram sample of ﻿$HCOOH$﻿?

##### Comparing Quantities

7) The chemical formula of Ibuprofen is ﻿$C_{13}H_{18}O_2$﻿. Evaluate the following statement.

"﻿$154.7\text{ g}$﻿ is a larger sample than ﻿$3.612\times10^{23}$﻿molecules"

True or false? Write below.
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8) Three samples of Carbon Dioxide, ﻿$CO_{2(g)}$﻿, are measured. Arrange the samples from the smallest quantity to the largest quantity by listing the sample number and using a comparison symbol.

For example: ﻿$\ 1<2<3\$﻿, if Sample ﻿$3$﻿ is the largest and Sample ﻿$1$﻿ is the smallest.

﻿$\begin{array}{|c|c|} \hline \\[-1em] \text{Sample}&\text{Quantity}\\[-1em]\\ \hline \\[-1em]1&6.02\times 10^{23}\text{ moles}\\[-1em]\\ \hline \\[-1em]2&6.02\times10^{23}\text{ grams}\\[-1em]\\ \hline \\[-1em]3&6.02\times10^{23}\text{ molecules}\\[-1em]\\ \hline \end{array}$﻿

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9) Four samples of water are measured. Arrange the samples from the smallest quantity to the largest quantity by listing the sample number and using a comparison symbol.

For example: ﻿$A\ <\ B\ <\ C\ <\ D$﻿

﻿$\begin{array}{|c|c|} \hline \\[-1em] H_2O_{(l)}\text{ Sample}&\text{Quantity}\\[-1em]\\ \hline \\[-1em]A&0.3500\text{ g}\\[-1em]\\ \hline \\[-1em]B&0.1000\text{ mol}\\[-1em]\\ \hline \\[-1em]C&1.084\times10^{24}\text{ molecules}\\[-1em]\\ \hline \\[-1em]D&18.00\text{ g}\\[-1em]\\ \hline \end{array}$﻿

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##### Molar Masses

10) A ﻿$0.2500\text{ mol}$﻿ sample of a certain element is determined to have a mass of ﻿$7.7426\text{ g}$﻿. What is the molar mass ﻿$\left(\frac{g}{mol}\right)$﻿ of the substance?

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11) Write the chemical symbol of the element from question ﻿$10)$﻿.

12) What is the molar mass ﻿$\left(\text{g}\cdot\text{mo}l^{-1}\right)$﻿ of a sample if ﻿$2.54\times10^{22}$﻿ molecules has a mass of ﻿$2.00\times10^{-2}\text{ kg}$﻿? ﻿$\left(1\text{ kg}=1000\text{ g}\right)$﻿