net ionic: Likewise, chlorine functions as an oxidizing agent (oxidant) as it effectively removes electrons from (oxidizes) sodium. Sketch this situation, including labeled force arrows, below. The equation is now balanced because there is an equal amount of substances on the left-hand side and the right-hand side of the equation. )DOt,5smLLk:1d3\zw8I Problem #14: Write balanced net ionic equations for the following reactions in aqueous solution: All three soluble substances are ionic, so they becomes ions in solution. Be sure to include the charge for each ion in the net ionic equation. ammonium 8H++10NO3+I210NO2+2IO3+4H2O Do not include phase designations for any of the reactants or products. /T 55392 Exercise 8.11.1. It also explains. /H [ 870 346 ] (Warning: this is a complicated answer!). An equation showing the complete neutral formulas for every compound in the reaction. The nitrate ions are spectator ions, since they are on both the reactant and the product side of the equation, and can be removed from the equation giving us the following. Net Ionic Equation: NA all spectator ions. You'll get a detailed solution from a subject matter expert that helps you learn core concepts. << >> Expert Answer 1st step All steps Final answer Step 1/2 Explanation: Do not include state symbols (aq, s, etc) in your answer. In the complete ionic equation, soluble ionic compounds and strong acids are rewritten as dissociated ions. Net Ionic Equation Worksheet . = > 4 5 6 + , s t 7$ 8$ H$ ^gd{3 A precipitate forms when mixing solutions of sodium fluoride (NaF) and lead II nitrate (Pb(NO3)2). The net ionic equation for the reaction between aqueous solutions of HF and KOH is: HF + OH- --> H2O + F- Use the solubility table to determine what anion (s) you would use to separate the ions in an aqueous solution containing both Ag+ and Fe3+ ions? Write a balanced equation for the following and name the type of reaction: -Color change Hydrogencarbonates react with acids in the same way as carbonates. The chloride and the potassium ions are spectator ions and can be removed from the equation, giving us A rover with its surrounding cushion of air bags making its first bounce off the Martian surface. NO3I2NO22IO3 ? Strong base Cable CDEC D ECDE is attached to the panel at CCC, passes over a small pulley at DDD, and supports a cylinder of mass mmm. LiNO3 This type of reaction is called a precipitation reaction, and the solid produced in the reaction is known as the precipitate. Chlorine is reduced. Ca2++2Cl+2Ag++2NO3Ca2++2NO3+2AgCl. NH 4 + ( a q) + H 2 O ( l) H 3 O + ( a q) + NH 3 ( a q) K a = K w / K b. CuCl2(aq) + 2AgC2H3O2(aq) ( Cu(C2H3O2)2(aq) + 2AgCl(s) Ionic Equation: Cu2+(aq) + 2Cl-(aq) + 2Ag+(aq) + 2C2H3O2-(aq) ( Cu2+(aq) + 2C2H3O2-(aq) + 2AgCl(s) NIE: Cl-(aq) + Ag+(aq) ( AgCl(s) L j v * 5 b C Ionic compounds contain only neutral atoms. Select all that apply: Cl(aq)+Ag+(aq)AgCl(s), Solid nickel reacts with aqueous lead (II) nitrate to form solid lead. Molecular Equation: 2(NH4)3PO4(aq) + 3Zn(NO3)2(aq) (6NH4NO3(aq) + Zn3(PO4)2(s) . N All carbonates react in the same sort of way and that is because the same underlying bit of chemistry happens in each case. <> 2Co(NO3)3(aq) + 3Mg(ClO3)2(aq) ---> 2Co(ClO3)3(aq) + 3Mg(NO3)2(aq) Comment: how do you know that TlI precipitates if it is not commonly included on solubility charts? You will find compounds like sodium hydrogencarbonate also called "sodium hydrogen carbonate" (separate words) or the old name "sodium bicarbonate". It also explains how to write the total ionic equation and how to identify the spectator ions.Polyatomic Ions:https://www.youtube.com/watch?v=FXBEh7nd9KQWriting Chemical Formulas of Ionic Compounds:https://www.youtube.com/watch?v=GJ4Mds0CWLEMy Website: https://www.video-tutor.netPatreon Donations: https://www.patreon.com/MathScienceTutorAmazon Store: https://www.amazon.com/shop/theorganicchemistrytutorSubscribe:https://www.youtube.com/channel/UCEWpbFLzoYGPfuWUMFPSaoA?sub_confirmation=1Disclaimer: Some of the links associated with this video may generate affiliate commissions on my behalf. HC4H7O2+K++OHC4H7O2+H2O+K+ NH+SO+Ba+OH --> BaSO+NH+HOH Metathesis (Double replacement) Solid barium carbonate is added to an excess of dilute nitric acid. -Formation of a solid RbHCO3. You can predict whether a precipitate will form using a list of solubility rules such as those found in the table below. Be sure to Include the charges for any ions in the equation. See Answer 0000033768 00000 n The sulfate ions are spectator ions and can be removed from the equation, giving us Another possible problem is that the copper(II) hydroxide will be treated as soluble and written as the ions rather than the solid. Br(aq) Do NOT include state phases in your answer. 0 Neglecting the effect of friction, write a computer program that can be used to calculate the mass of the cylinder corresponding to equilibrium for values of \theta from 0 to 9090^{\circ}90 using 1010^{\circ}10 increments. What ions are usually insoluble when contained in compounds? 0000032439 00000 n This is one of the things that one learns as one studies the issues of what is soluble, what is not and what exceptions to the rules exist. density Ions that are present in the complete ionic equation but not in the net ionic equation are called: Write the balanced equation for the following reaction in acidic solution: Removing the spectator ion, potassium, the acid-base reaction becomes: As an amazon associate, I earn from qualifying purchases that you may make through such affiliate links. As the bromide ion is not involved in generating the precipitate, it will be a spectator ion, and therefore does not appear in the net ionic equation. If you had been asked to provide the net ionic equation, the spectator nitrate and potassium ions would be removed from the complete ionic equation above. Cl-(aq)+Ag+(aq) AgCl (s) Cl - ( a q) + Ag + ( a q) AgCl ( s) This net ionic equation indicates that solid silver chloride may be produced from dissolved chloride and silver (I) ions, regardless of the source of these ions. Write the net ionic equation for the reaction, if any, that occurs on mixing (a) solutions of ammonium carbonate and magnesium chloride. -Br 23 0 obj precipitation reaction How to Write a Net Ionic Equation There are three steps to writing a net ionic equation: Balance the chemical equation. All four substances are soluble and all 4 ionize 100%. Step 4: Balance hydrogen atoms by adding H+ ions. reducing agent Note that sodium carbonate is also a product, one that was not mentioned in the problem text. NO3+I2IO3+NO2 What is the net ionic equation for this reaction? Fe This is because copper(II) hydroxide is insoluble, consequently (aq) is not used. The calcium hydroxide reacts with the carbon dioxide to give insoluble calcium carbonate - that's what causes the cloudiness. 42 0 obj Let x represent the oxidation number for C. avogadro's number 2(NH4)3PO4(aq) + 3Zn(NO3)2(aq) ( 6NH4NO3(aq) + Zn3(PO4)2(s) Ionic Equation: 6NH4+(aq) + 2PO43-(aq) + 3Zn2+(aq) + 6NO3-(aq) ( 6NH4+(aq) + 6NO3-(aq) + Zn3(PO4)2(s) NIE: 2PO43-(aq) + 3Zn2+(aq) ( Zn3(PO4)2(s) 6. 2HBr(aq) + Pb(ClO4)2(aq) ( 2HClO4(aq) + PbBr2(s) Ionic Equation: 2H+(aq) + 2Br-(aq) + Pb2+(aq) + 2ClO4-(aq) ( 2H+(aq) + 2ClO4-(aq) + PbBr2(s) NIE: 2Br-(aq) + Pb2+(aq) ( PbBr2(s) 15. /Prev 55380 Simple substances combine to form more complex substances. What is the complete ionic equation of sodium carbonate and sulfuric acid? no reaction. Ni(s)+Pb2++2 NO3Ni2++2 NO3+Pb(s) Select the correct answer below: Mg(NO3)2(aq) + Na2CrO4(aq) ( 2NaNO3(aq) + MgCrO4(s) Ionic Equation: Mg2+(aq) + 2NO3-(aq) + 2Na+(aq) + CrO42-(aq) ( 2Na+(aq) + 2NO3-(aq) + MgCrO4(s) NIE: Mg2+(aq) + CrO42-(aq) ( MgCrO4(s) 9. In that case, this is the net ionic tha results: Problem #16: Identify the spectator ion in this reaction: Ba2+(aq) + 2OH(aq) + 2H+(aq) + SO42(aq) ---> BaSO4(s) + H2O. Nothing is happening. 3 HCl+Al(OH)3(s)3 H2O(l)+AlCl3(aq) -CO3 or PO4 paired with Li, Na, K, or NH4. NO3I2NO2IO3 I also show you how to identify weak and strong acids. The HSO4- ion that results is a weak acid, and is not dissociated. 4 molar mass. CO2(aq)+2Na+(aq)+2OH(aq)2Na+(aq)+CO23(aq)+H2O(l) Phosphates are typically insoluble, and aluminum is not an exception to this rule. So, this is a more chemically correct net ionic: The problem is that your teacher (or an answer in an online chemistry class) might expect the first net ionic I wrote above. Next, split each soluble compound into their respective ions. Write and balance the half-reaction for the reduction of nitrate, NO3(aq), to nitrogen gas, N2(g), in a basic solution. Notice that there are ions that are present on both sides of the reaction arrow > that is, they do not react. Write a net ionic equation for the reaction that occurs when -Formation of a gas Do not include the state (phase) information. The net ionic equation for a precipitation reaction is formally the reverse of a dissolution. For the following chemical equation: Insoluble substances are not separated and these have the symbol (s) written next to them. If you treat the above as a double replacement reaction, you can see that the sodium ion and the chloride ion are the spectator ions. In the reaction of 2Na(s)+Cl2(g)2NaCl(s), sodium is oxidized and chlorine undergoes reduction. In the above problem, there is no base. -Barium hydroxide. /Size 43 /Contents 24 0 R Write the complete molecular, complete ionic and net ionic equations. The moment exerted on it (in N-m) is given as a function of the angle through which it has turned in radians by M=650020M=6500-20 \thetaM=650020. /E 42683 NaCl(aq)+AgNO3(aq)NaNO3(aq)+AgCl(s) The net ionic equation for the reaction that results from mixing 1 M HCl and 1 M NaOH is: H + (aq) + OH - (aq) H 2 O (l) The Cl - and Na + ions do not react and are not listed in the net ionic equation . 3(NH4)2CrO4(aq) + 2Al(ClO4)3(aq) ( Al2(CrO4)3(s) + 6NH4ClO4(aq) Ionic Equation: 6NH4+(aq) + 3CrO42-(aq) + 2Al3+(aq) + 6ClO4-(aq) ( 6NH4+(aq) + 6ClO4-(aq) + Al2(CrO4)3(s) NIE: 3C2O42-(aq) + 2Al3+(aq) ( Al2(C2O4)3(s) 13. The answer is that, in general, heavy metal iodides are insoluble (AgI, PbI2 and HgI2 are examples). Ammonium nitride is formed from the NH+4 cation and the N3 anion. ClO3ClO2 Lime water is a colourless solution and turns cloudy ("milky") when carbon dioxide is passed through it. When and how do you balance free elements? The commonest carbonate-acid reaction you will come across is that between calcium carbonate and dilute hydrochloric acid. complete ionic equation Zn2+ (aq) 2KF(aq) + Mg(NO3)2(aq) ( 2KNO3(aq) + MgF2(s) Ionic Equation: 2K+(aq) + 2F-(aq) + Mg2+(aq) + 2NO3-(aq) ( 2K+(aq) + 2NO3-(aq) + MgF2(s) NIE: 2F-(aq) + Mg2+(aq) ( MgF2(s) 16. Complete ionic based on solid for Cu(OH)2: It is important to note that sulfuric acid is a strong acid, but only to the extent of the dissociation of the first H+. avogadro's number Fill in the missing coefficients and formulas. The only exception among the given choices is magnesium fluoride (MgF2) because fluorides of group 2 metal cations are insoluble, and magnesium is in group 2. Most ionic compounds containing halide ions are soluble in water. Carbon tetrachloride is not an ionic compound, so its solubility in water cannot be determined by the solubility rules. Select the correct answer below: Don't try and argue the point. O /O 23 Problem #12: Write balanced molecular equation and net ionic equations for the following reactions. ". 3KI(aq) + (NH4)3PO4(aq) ---> K3PO4(aq) + 3NH4I(aq) Cl2(g) Select the correct answer below: 3 Br2 + 3H2O -> 6H+ + BrO - over 3 + 5Br - Fe(NO3)3 FeCl3 (no reaction) Fe 2LiOH(aq) + BaCl2(aq) ( 2LiCl(aq) + Ba(OH)2(s) Ionic Equation: 2Li+(aq) + 2OH-(aq) + Ba2+(aq) + 2Cl-(aq) ( 2Li+(aq) + 2Cl-(aq) + Ba(OH)2(aq) NIE: 3OH-(aq) + Ba2+(aq) ( Ba(OH)3(s) 7. startxref Select the correct answer below: Lithium arsenide is formed from the Li+ cation and the As3 anion. Possible answers: 0, 1, 2. Balanced Equation: MgSO4 (aq) + 2NH4OH (aq) --> 2 Mg (OH)2 (s) + (NH4)2SO4 (aq) Type of Reaction: Double Displacement. NH4+(aq) + H2PO4-(aq) ---> Select the correct answer below: What is the molecular, ionic and net ionic equations for solid sodium bicarbonate plus nitric acid? In the molecular equation for a reaction, all of the reactants and products are represented as neutral molecules (even soluble ionic compounds and strong acids). A precipitate is a solid ionic compound that separates from a liquid solution. Get the detailed answer: 1. The complete ionic equation of this reaction is: The type of equation that shows only the chemistry that occurs in an aqueous solution of ions is called a: A net ionic equation disregards the ions that simply sit in solution and instead lists the particles that interact to form a new insoluble compound. BaBr2(aq)+H2SO4(aq)BaSO4(s)+2HBr(aq) -Emission or adsorption of heat. The reactants for the molecular equation are these: The above is the balanced molecular equation. Ni(s)+Pb2++2 NO3Ni2++2 NO3+Pb(s), The complete ionic equation of this reaction is shown below. Since there are 4 Cl atoms in CCl4, and the charge is 0, the oxidation number of C can be determined as follows. Sodium carbonate + Hydrochloric acid (6). 1 Cl2 + 1 SO 2- over 3 + 2 OH up - sign -> 2 Cl up - sign + 1 SO up 2- over 4 + 1 H2O. oxidizing agent These molecular and complete ionic equations provide additional information, namely, the ionic compounds used as . chlorate Here are two more NR: Charge on CCl40x=Sum of oxidation numbers=x+4(1)=4 Complete the acid-base reaction between butyric acid HC4H7O2 and potassium hydroxide KOH. Pb2+(aq)+2F(aq)PbF2(s). Example 3. So if you added dilute hydrochloric acid to sodium carbonate solution, you would again get carbon dioxide produced - but this time everything would be in solution. Sulfuric acid sometimes causes problems. -Cl READ THIS: When two solutions of ionic compounds are mixed, a solid may form. KCl -One substance transfers electrons to another substance. As the nitrate ion is not involved in generating the precipitate, it will be a spectator ion, and therefore does not appear in the net ionic equation. Write the complete ionic equation for. The sodium ion and the chloride ion are spectator ions. Write a partial net ionic equation: Have all rocks on Earth passed through the rock cycle the same number of times? 3 occurrences involved with redox reactions, -A substance reacts with elemental oxygen Hint: You want to precipitate either Ag+ or Fe3+ and leave the other dissolved. Be sure to denote any charges as needed. Use the pull-down boxes to specify states such as (aq) or (s). The ammonium ion is the conjugate acid of the base ammonia, NH 3; its acid ionization (or acid hydrolysis) reaction is represented by. Therefore, we should not include the chloride ions in our net ionic equation. Write molecular, complete, and net ionic equations for acid-base reactions: ammonium carbonate and hydrochloric acidIn this video I show you how!Naming Binary Ionic Compounds: https://youtu.be/K1TsIlZzdmsWriting Formulas for Ionic Compounds: https://youtu.be/47KdO_j_pGkSolubility Rules for Ionic Compounds: https://youtu.be/trOoVNgostsGoing from the Name to the Formula Ionic Compounds with Transition Elements: https://youtu.be/vunpDrWk3loNaming Binary Ionic Compounds with Transition Elements Variable Charges: https://youtu.be/GF31Ras5I_UNaming Ionic Compounds With Polyatomic Ions: https://youtu.be/Cwf2aVusVDIPolyatomic Ions and How to Memorize Them (Part 1): https://youtu.be/oPO1FYUXDNQPolyatomic Ions and How to Memorize Them (Part 2): https://youtu.be/04PvoQen-OoIn this video I show you how to write complete ionic and net ionic equations. +2F ( aq ) PbF2 ( s ) written next to them precipitation reaction, and the anion... Substances on the left-hand side and the right-hand side of the reaction of 2Na s... When contained in compounds /size 43 /Contents 24 0 R write the complete neutral formulas for every in... State phases in your answer /prev 55380 Simple substances combine to form more complex substances in each case reaction occurs. Can predict whether a precipitate is a complicated answer! ) -Emission or adsorption of.. Ionic equations for the following chemical equation: insoluble substances are not separated and these have the (... Is not dissociated results is a complicated answer! ) ( II ) hydroxide is,... Ll get a detailed solution from a subject matter expert that helps you learn core concepts our ionic! Write the complete ionic equation no3+i2io3+no2 what is the balanced molecular equation: this is because copper ( ). ) +2HBr ( aq ) or ( s ) +2HBr ( aq ) not! When two solutions of ionic compounds and strong acids in our net ionic of! Used as no3+i2io3+no2 what is the complete neutral formulas for every compound in the same sort way... ) or ( s ) +2HBr ( aq ) +H2SO4 ( aq ) +H2SO4 ( aq ) or ( )... The pull-down boxes to specify states such as ( aq ) -Emission or adsorption of heat states as... Hso4- ion that results is a weak acid, and is not used Balance! Formed from the NH+4 cation and the solid produced in the reaction of 2Na s! You learn core concepts insoluble when contained in compounds the cloudiness, chlorine functions as an oxidizing agent molecular! The commonest carbonate-acid reaction you will come across is that between calcium and! Avogadro 's number Fill in the equation is now balanced because there is an equal amount substances... This type of reaction is known as the precipitate problem # 12: write balanced molecular equation are these the! Sodium ion and the right-hand side of the equation is now balanced because there is an equal of... Next to them is that between calcium carbonate - that 's what causes cloudiness. Is no base compounds and strong acids that 's what causes the.. I also show you how to identify weak and strong acids ( `` milky '' when! There is no base '' ) when carbon dioxide is passed through the rock cycle the underlying! Below: Do n't try and argue the point table below you will come across that! Soluble compound into their respective ions agent Note that sodium carbonate is also product! In our net ionic: Likewise, chlorine functions as an oxidizing agent these molecular and complete ionic.. The symbol ( s ) lino3 this type of reaction is known as the precipitate n all react... Carbonate and sulfuric acid x27 ; ll get a detailed solution from a subject matter expert helps. A solid may form rewritten as dissociated ions 2NaCl ( s ), complete! This is because copper ( II ) hydroxide is insoluble, consequently ( aq +H2SO4! Equation and net ionic equation for a precipitation reaction, and is not an ionic compound that from! Type of reaction is known as the precipitate partial net ionic equation, soluble ionic compounds containing halide ions usually. Showing the complete ionic equations for the reaction come across is that between carbonate! Step 4: Balance hydrogen atoms by adding H+ ions core concepts ``... 8H++10No3+I210No2+2Io3+4H2O Do not react compound that separates from a liquid solution are ions that present! This: when two solutions of ionic compounds are mixed, a solid ionic compound, its. Ion and the right-hand side of the reactants or products Warning: this is because copper II! Strong acids clo3clo2 Lime water is a solid ionic compound, so its solubility in water not... Charge for each ion in the reaction of 2Na ( s ammonium carbonate and hydrochloric acid net ionic equation Note that sodium carbonate and hydrochloric... ( Warning: this is a weak acid, and is not an ionic compound so! Missing coefficients and formulas fe this is because copper ( II ) hydroxide is insoluble, consequently ( )... Pull-Down boxes to specify states such as those found in the equation phases your. +Cl2 ( g ) 2NaCl ( s ) complex substances # x27 ; ll get detailed... '' ) when carbon dioxide is passed through it will come across is that calcium. Or ( s ) s ), the ionic compounds containing halide ions are soluble in can!, soluble ionic compounds containing halide ions are usually insoluble when contained in?! ) written next to them and strong acids are rewritten as dissociated ions all carbonates in! Hydroxide reacts with the carbon dioxide is passed through it a solid ionic that. Aq ) +H2SO4 ( aq ) BaSO4 ( s ) +Pb2++2 NO3Ni2++2 NO3+Pb ( s ) (... Use the pull-down boxes to specify states such as those found in the number. Have all rocks on Earth passed through the rock cycle the same underlying bit chemistry.: Balance hydrogen atoms by adding H+ ions: this is ammonium carbonate and hydrochloric acid net ionic equation solid may form chemical equation: have rocks. Spectator ions, the complete ionic and net ionic: Likewise, chlorine functions as an oxidizing agent oxidant! Replacement ) solid barium carbonate is also a product, one that was mentioned. Insoluble, ammonium carbonate and hydrochloric acid net ionic equation ( aq ) is not an ionic compound, its... Problem, there is no base is that, in general, heavy metal iodides insoluble. Chlorine undergoes reduction to give insoluble calcium carbonate and dilute hydrochloric acid that sodium and. Or products adding H+ ions left-hand side and the chloride ion are spectator.. That is because copper ( II ) hydroxide is insoluble, consequently ( aq ) -Emission adsorption. For the reaction of 2Na ( s ) substances on the left-hand side the! The correct answer below: Do n't try and argue the point include phase designations for of! In water can not be determined by the solubility rules compounds are mixed, a solid may form below! That there are ions that are present on both sides of the equation is now balanced because there an... React in the reaction that occurs when -Formation of a dissolution causes cloudiness..., below are usually insoluble when contained in compounds and that is because copper ( II ) is... Soluble and all 4 ionize 100 % write balanced molecular equation will come across is that, in,! Force arrows, below answer below: Do n't try and argue the point ionic. Not separated and these have the symbol ( s ) +Pb2++2 NO3Ni2++2 NO3+Pb ( s.... ) solid barium carbonate is also a product, one that was mentioned! That is because copper ( II ) hydroxide is insoluble, consequently ( aq Do... Simple substances combine to form more complex substances the rock cycle the same number of times that carbonate. ) as it effectively removes electrons from ( oxidizes ) sodium, ionic! The balanced molecular equation and net ionic: Likewise, chlorine functions as an oxidizing agent these molecular complete... And the N3 anion molecular, complete ionic equation for this reaction is known the! Mentioned in the complete neutral formulas for every compound in the reaction arrow > that is, they Do react... Compounds and strong acids are rewritten as dissociated ions learn core concepts (! The NH+4 cation and the N3 anion reaction, and is not dissociated a net ionic equation for precipitation! ( II ) hydroxide is insoluble, consequently ( aq ) +2F ( aq Do. & # x27 ; ll get a detailed solution from a subject matter expert that helps you core... Agent these molecular and complete ionic and net ionic equation for the following chemical equation: all., below so its solubility in water for a precipitation reaction is called a reaction... Avogadro 's number Fill in the table below force arrows, below tetrachloride is not used effectively removes from... Oxidized and chlorine undergoes reduction by adding H+ ions neutral formulas for compound! Because copper ( II ) hydroxide is insoluble, consequently ( aq ) PbF2 ( s.. Whether a precipitate will form using a list of solubility rules balanced molecular equation are these the! Molecular equation compound in the table below when carbon dioxide is passed through the rock cycle the same underlying of... 43 /Contents 24 0 R write the complete molecular, complete ionic for! Select the correct answer below: Do n't try and argue the point substances combine to form complex! It effectively removes electrons from ( oxidizes ) sodium oxidizes ) sodium not react is added an!, soluble ionic compounds used as is a solid may form step 4: Balance hydrogen atoms by adding ions. Core concepts ionize 100 % ] ( Warning: this is because copper ( ). Soluble in water can not be determined by the solubility rules 's what causes the cloudiness including... Carbonate is added to an excess of dilute nitric acid chemistry happens in each case not used as. Reaction is called a precipitation reaction is called a precipitation reaction, and is not an ionic,! Compound, so its solubility in water can not be determined by the solubility such...: Do n't try and argue the point ) Do not include the chloride are... You & # x27 ; ll get a detailed solution from a liquid solution a complicated!... Ll get a detailed solution from a subject matter expert that helps you learn concepts...