Life Science Mid-Term FLASHCARDS

Model cell membrane structure; describe functions and orientation of phospholipid bilayer; cholesterol; channel proteins; glycoproteins based on chemical properties of polar (hydrophilic) and non polar (hydrophobic) regions.

Distinguish between passive (no energy used) and active (energy used) transport.

Apply the concepts of diffusion and osmosis to cells; Define a hypertonic, hypotonic and isotonic solution and predict how these would affect a cell.

Interpret tests for starch and glucose using Logol's and Benedict's indicators.

Explain​ why cells use facilitated transport (facilitated diffusion) for some substances.

Define a mole as an amount that is 6.02 x 1023 and is used to group particles such as atoms, ions and molecules

Use the mole concept to convert between moles, particles, mass and concentration; measure molecular quantities on an electronic balance.

Use​ units of concentration (g/L OR g/dm3, mole/L OR mol/dm3); produce solutions of specific concentrations.

​Determine the concentration of a solution that is the isotonic equivalent of a potato using osmosis; calculate % change on mass; graph and interpret the results.

Concentration


  • measures solute to solvent ratio (i.e. how much solute is dissolved in how much solvent?)

  • For aqueous (liquid) solutions, we measure  solutes in grams or moles and solvent (water) in Liters or dm3 (1L=1dm3; dm3 is unit used in IB Chem)

  • Standard measures of concentration: 

g/L   (same as g/dm3)

        mol/L (same as mol/dm3)

wait… what’s a mol (mole)?

Particles, like atoms, ions and molecules are VERY VERY SMALL!


It doesn’t make sense to try and keep track of individual particles (atoms, ions or molecules) because there is no way to measure them…







So we group them into a large number whose mass can be measured in grams


1 pair of atoms is


2 atoms!

1 dozen atoms is


12 atoms!

1 MOLE of atoms is


602,214,199,000,000,000,000,000 atoms

("602 sextillion")

or

6.02 x 1023 atoms


Here is 1 mole of carbon atoms

(or 6.02x1023 atoms of C)


note: the mass 

is 12.00 grams

So what exactly is a Mole?

A spy?

 A burrowing animal?

A spot of skin pigmentation?






The Chemical Mole

is an amount containing

6.02 x 1023

particles.


determining molar mass 

(molar mass = mass of 1 mole of any substance)


Molar mass is simply the average atomic mass of any element (or elements) as found on the periodic table (see above) measured in grams. Units of molar mass is measured in g/mol

example: what is the molar mass of...



Oxygen ?


Carbon?


Water (H2O)?


Magnesium?

let’s practice!


determine the molar masses of the following:

carbon dioxide (CO2)

ammonia (NH3)

table salt (NaCl)

calcium carbonate (CaCO3)

glucose (C6H12O6)

MOLES

symbol: n

units: mol


Particles

(atoms/ions/ molecules)

units are type of particle



Moles ⇔ Particles


x 6.02 x 1023


÷ 6.02 x 1023


use GUESS: given → unknown → equation → substitute → solve 



How many ions (particles) of sodium are in 2 mol?

     




If there are 2 x 1023   atoms of Copper, is this a mole?

    


given: 2 mol Na

unknown: ions (particles) of Na?

equation: moles x 6.02 x 1023 ions/mole (follow arrows on mole map)

substitute: 2 mol x 6.02 x 1023 ions/mol

solve: 1.20 x 1024  Na ions 


given: 2 x 1023 atoms Cu

unknown: moles of Cu?

equation: atoms (particles) ÷ 6.02 x 1023 ions/mole (follow arrows on mole map)

substitute: 2 x 1023 atoms ÷ 6.02 x 1023 atoms/mol

solve: 0.33 mol Cu (it is 1/3 of a mole of Cu)

more practice! - moles/concentration


Calculate the concentrations of the following:

  1. 1.2 mol of NaCl dissolved in 1.0 L of water

  2. 5.3 mol of NH3 dissolved in 0.5 L of water

  3. 3.0 mol of CaCO3 dissolved in 2.3 L of water

Calculate the moles of the following:

  1. sodium hydroxide (NaOH) dissolved in 0.4 L of a 1.2 mol/L solution? 

  2. sulfuric acid (H2SO4) dissolved in 1.3 L of a             2.0 mol/L solution

  3. glucose (C6H12O6) dissolved in 4.0 L of a                 3.0 mol/L solution        


now for some more challenging problems!


A beaker of water contains 180 g of water. How many molecules of water does the beaker contain?


If you add 85 g of MgCl2 to 4.3 L of water, what would be the final concentration (in mol/L)?


A 6.7 L solution of HCl has a concentration of 0.2 mol/L. How many molecules of HCl is dissolved in the solution?


*hint: for all problems, you need to go through moles!!

saline solution challenge


Your help is needed -  100 ml of an IV saline drip solution is required for a sick patient. The concentration of the IV saline solution needs to be 0.1 mol/L of NaCl.


Equipment: tray, 100 ml volumetric flask, rubber stopper, electronic balance, weighing boat, NaCl, beaker of distilled water, plastic dropper, plastic funnel.


Your completed solution will undergo quality control by your teacher. Show all calculations on sheet of paper provided. 

Potato Osmosis Lab 


Aim: to determine the precise concentration of a salt (NaCl) solution that is the isotonic equivalent of your potato




cut pieces of potato using potato corer; measure initial mass of each piece; then soak in salt solutions


potato pieces will be soaked for 30 minutes in five different molar concentrations of salt (NaCl) solution

calculating % change


% change equation:

                           final - initial  x 100 

                                 initial




example: 

The change in average global surface temperature has gone from 13.90 to 14.69℃. Calculate the % change in temperature.


final = 14.69℃                      14.69 - 13.90  x  100  = 5.68% increase

initial = 13.90℃                          13.90