Mole volume calculation Nat 5

Example discussed in video (taken from SQA 2016 National 5 Past Paper).
ppq

Have a go at the following example once you’re confident with the method discussed in the video:

MgCO3 + 2 HCl -> MgCl2 + H2O + CO2

1 mole of carbon dioxide has a volume of 24 litres.

Calculate the volume of carbon dioxide produced when 42.15g of magnesium carbonate reacts with excess hydrochloric acid.

Science Of A Night Out

To kick off 2018 in style, S1 Science Club have started a 3 month long STEM project where they’ll be investigating the science behind their favourite night out activities such as ice skating, discos and ten-pin bowling.

In the first week, we focused on the preparation for the night out and why it’s important to brush our teeth before consuming loads of sweets and fizzy juice. Pupils covered half of an egg in toothpaste and left the other half exposed and placed the egg in Coca Cola over the weekend. The following week we analysed the egg and saw first-hand the effect fizzy juice can have on our teeth!

Here’s some keen scientists explaining their investigation:

Calculating Average Rate of Reaction

Average Rate calculations are common questions in National 5 exams. They seem to crop up in 3 forms: a table, a graph or a multiple choice question.

The example I work through in the video is from a table of values from an experiment. During a reaction, the volume of gas produced is measured at 30 second intervals and the results are displayed in the table provided.

The exam question asks you to calculate the average volume between 60 and 90 seconds (a 30 second time period). What you have to do is see how much gas is produced during this time period, and divide it by the time period (in seconds).

This will give you the rate, in cm3/s.

Percentage Composition

A percentage composition calculation is used to calculate how much of the total mass of a compound is accounted for by a particular atom.

For example, in the above video the question has asked to calculate what percentage of the total mass of KMnO4 is accounted for by K (potassium).

National 5 – Volumetric Titration Calculations (try saying that 3 times fast)

Calculations are a key part of National 5 Chemistry (and chemistry in general). Love ’em or hate ’em, you still gotta do ’em.

 

An important part of carrying out calculations is actually understanding what the question is asking and how to tackle it.

Below is a detailed walkthrough of a Volumetric Titration Calculation, where you’re asked to calculate the concentration of a solution but you’re only given a volume. Remember, to calculate number of moles, concentration or volume of a solution you use the following triangle:

Image result for n=cv triangle

However, you need 2 values to be able to calculate the unknown. What the video explains is how you can work out the number of moles of a known solution and use that value (depending on the mole ratio) in your c=n/v calculation.

You can do it!

Mr S

Neutralisation

Neutralisation, fundamentally, is the reaction of an acid and a base to give a neutral substance (water) and a salt.

The hydrogen ions from the acid and the hydroxide ions from the alkali join in equal concentrations to produce water molecules. What is left is the anion (negative ion) from the acid and the cation (positive ion) from the alkali, which also join to produce your salt.

For example,

HCl + NaOH -> H2O + NaCl

Acid + Base -> Water + Salt

 

When you take an indigestion tablet such as Rennies or Gaviscon, this same reaction happens in your stomach and oesophagus when you have acid reflux. The tablet neutralised any excess stomach acid to reduce heartburn.

 

Screaming Jellybaby!

No Jellybabies were harmed in the making of this video.

 

 

Since demonstrating the screaming jellybaby on the first day of term, I get asked on a near daily basis to do it again. After watching the video, you can clearly see why!

The reaction itself is simple: heat up a white powder known as potassium chlorate (which contains potassium, chlorine and oxygen) until it is molten, and drop in an unlucky jellybaby. The rest is history.

The reaction demonstrates how much energy is stored in sugary sweets such as jellybabies and gummy bears, as we observed the colourful display of light and gas being produced. The molten potassium chlorate is rapidly oxidising (giving electrons to) the carbohydrate filled jellybaby which causes the spectacular reaction.

Further reading can be done on the Royal Society of Chemistry website.

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