ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel

Molarity Formula: Sample Problems with Solutions and a Quiz (Complete Tutorial)

Updated on February 7, 2013
A reagent bottle of concentrated HCl with a Molarity of 6.
A reagent bottle of concentrated HCl with a Molarity of 6.

First, what is molarity?

Molarity is one of the several ways to describe the concentration of a solution. It is basically how many moles of the solute are present in your solution.

You can calculate the Molarity of your solution using this formula:

M = n/V

Where M is the Molarity, n is the number of moles of the solute and V is the volume of your solution.

The chemicals in your laboratory have specific Molarity. Hence, your teacher will insist that you learn to compute the Molarity of your solution. He or she might even ask to prepare a solution with a certain Molarity.

Molarity Formula in Action: Sample Problem # 1

What is the molarity of a 2 L solution containing 20 g of sodium chloride?

To solve this problem, we must list down the given quantities first based on the Molarity formula.

M = n/V

Given:

Volume of solution (V) = 2 L

Moles of Solute (n) = not given

Molarity = not given

There are two unknowns in the Molarity formula: moles of solute and the Molarity. Since we are asked for the Molarity, we should look for the moles of solute first.

The problem tells us that there is 25 g of NaCl in the solution. Using your previous knowledge about molar mass, we can calculate the number of moles of the solute using dimensional analysis.

Let us calculate the molar mass of NaCl first.

Na › 23 g

Cl › 35 g

Molar Mass = 23 g + 35 g = 58 g

Then, let’s solve for the moles of NaCl.

25 g NaCl x 1 mole NaCl / 58 g NaCl =0.43 moles NaCl

We now have the number of moles of the solute. Finally, we can solve for the Molarity of this solution.

M = n/V

M = 0.43 moles NaCl / 2 L

M = 0.22 moles NaCl/L

M = 0.22 M

Therefore, the Molarity of the solution is 0.22.

Molarity Formula in Action: Sample Problem # 2

Let’s try another Molarity problem but with a shorter solution.

What is the Molarity of a half liter solution containing 5 g of copper sulfate?

M = n/V

Given:

Moles of solute = unknown

Volume of solution = 0.5 L

Mass of solute (CuSO4) = 5 g

Cu › 64 g

S › 32 g

O › 16 g x 4 = 64 g

Molar Mass of CuSO4 = 64 g + 32 g + 64 g = 160 g

5 g CuSO4 x 1 mole CuSO4 / 160 g CuSO4 = 0.03 moles CuSO4

M = n/V

M = 0.03 moles CuSO4 / 0.5 L

M = 0.6 M

Therefore, the Molarity of the solution is 0.06.

It’s Your Turn! Solve the following Molarity problems.

view quiz statistics

How to Determine the Amount of Solute Using the Molarity Formula

Okay, number three in the above quiz was a little bit tricky. I haven’t taught you that one yet.

If you got it right, you are very good! If not, don’t worry because I will teach you how to solve it.

The third problem is just the opposite of the first two sample problems. Let’s take a look at the problem again.

How many grams of NaCl is present in 2 liters of a 0.05 M brine solution?

First, identify what you can arrive with the given using the Molarity formula.

M = n/V

Given:

M = 0.05 M

V = 2 L

n = unknown

Let’s now solve for the number of moles of solute (n).

0.05 M = n/2 L

N = 0.1 moles NaCl

Now that we have the number of moles of NaCl, let’s use it to calculate the mass of NaCl in the solution.

0.1 moles NaCl x 58 g NaCl / 1 mole NaCl = 5.8 g NaCl

Therefore, there are 5.8 grams of NaCl in the solution.

Questions? Write a comment below and I'll answer as soon as I can.

Comments

    0 of 8192 characters used
    Post Comment

    No comments yet.

    working

    This website uses cookies

    As a user in the EEA, your approval is needed on a few things. To provide a better website experience, hubpages.com uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

    For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at: https://hubpages.com/privacy-policy#gdpr

    Show Details
    Necessary
    HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
    LoginThis is necessary to sign in to the HubPages Service.
    Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
    AkismetThis is used to detect comment spam. (Privacy Policy)
    HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
    HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
    Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
    CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
    Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the googleapis.com or gstatic.com domains, for performance and efficiency reasons. (Privacy Policy)
    Features
    Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
    Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
    Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
    Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
    Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
    VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
    PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
    Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
    MavenThis supports the Maven widget and search functionality. (Privacy Policy)
    Marketing
    Google AdSenseThis is an ad network. (Privacy Policy)
    Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
    Index ExchangeThis is an ad network. (Privacy Policy)
    SovrnThis is an ad network. (Privacy Policy)
    Facebook AdsThis is an ad network. (Privacy Policy)
    Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
    AppNexusThis is an ad network. (Privacy Policy)
    OpenxThis is an ad network. (Privacy Policy)
    Rubicon ProjectThis is an ad network. (Privacy Policy)
    TripleLiftThis is an ad network. (Privacy Policy)
    Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
    Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
    Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
    Statistics
    Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
    ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
    Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)