Which of the following statements does not conform to the definition of a mole?

  Which compound has the largest molar mass?

  Which of the following statements is true?

  Calculate the number of moles in 20.5 grams of sodium phosphate $(Na_3PO_4)$.

  

  Refer to the following chemical el;*waj-5w* ns* anfd)b6tcm x quation:2$NO_2(g)$ $\rightarrow$ $N_2O_4(g)$
At the same temperature and pressure,25.0$cm^3$ of nitrogen dioxide $(NO_2)$ gas is completely converted to dinitrogen tetroxide ($N_2O_4$) gas.What will be the volume of $N_2O_4$ produced?

  How many molecules are there ivk+st /c )e xzth)-vl6n 4.80 moles of glucose?

  20.0$cm^3$ of 0.100 mol $dm^{-3}$ NaOH were slowly added to a 10.0 $cm^3$ sample of 0.100mol $dm^{-3}$ HCl, and the pH was measured throughout the addition.
The equation for the reaction is as follows:NaOH$_{(aq)}$+HCl$_{(aq)}$$\rightarrow$NaCl$_{(aq)}$+$H_2O(l)$
The ionic product constant of water at $25^{\circ}C$ is $1.00\times10^{-14}$.
1.Calculate the number of moles of NaOH remaining at the end of the addition.  $\times10^{-3} mol$
2.Calculate the concentration of $OH^-$ at the end of the addition.  $mol\:dm^{-3}$
3.Using your value for $[OH^-]$ in (b), calculate the pH of the solution at the end of the addition.  

  Eugenol is an oily, aromatic liquid extracted from essential oils such as clov tcr x rmkhiu,6x6*+.qe and cinnamon. The mo*i .+r,txk66u qmh crxlecular formula of eugenol is $C_{10}H_{12}O_2$.
1.Calculate the molar mass of eugenol.  $g\:mol^{-1}$
2.Determine the percentage by mass of carbon, hydrogen, and oxygen in eugenol.C=  %H=  %O=  %
3.Predict the simplest, whole-number ratio of the atoms in eugenol.

  What is the percentage by mass of S in the compound sulfur dioxide $SO_2$

  Ascorbic acid $(C_6H_8O_6)$,or vitamin C, is a water-soluble vitamin that is essential for our immune system.
1.Calculate the number of moles in 2.50g of ascorbic acid.  mol
2.Calculate the mass of 1.28 moles of ascorbic acid.  g
3.Calculate the number of molecules in 50.0 g of ascorbic acid.  $\times10^{23}$
4.Determine the number of moles of carbon in 225 mg of ascorbic acid.  mol C

  Commercial vinegar contains a small peki j6led,5,tcxgqzxx l)xt01+t sq+:a, zu1brcentage of ethanoic acid. A student wishes to determine the concentration of ethanoic acid in vinegar. She titrates a sq1cet,xb1qudt+ +lag ,l 6x5t:xkz,0sx)i z j olution of ethanoic acid against a standard solution of potassium hydroxide of concentration $8.0\times10^{-4}$mol$dm^{-3}$.The equation for the reaction is $CH_3$$COOH_{(aq)}$+$KOH_{(aq)}$$\rightarrow$$CH_3$$COOK_{(aq)}$+$H_2O$(l)
A volume of 25.0$cm^3$ of vinegar was diluted with distilled water and made up to a volume of 250.0$cm^3$ in a volumetric flask. A burette was filled with the diluted solution.
25.0$cm^3$ of potassium hydroxide solution was added to a conical flask and three drops of phenolphthalein indicator added.
1.Ethanoic acid is considered a weak acid. Define the term ‘weak acid’.
2.The results of the titration are shown in the table below:

Trial	Volume of Titre$(cm^3)$
1	21.0
2	21.2
3	20.8

1.Using section 22 (Section 18- 2025 Syllabus) of the IB data booklet, identify the color at the endpoint.  
2.Calculate the concentration of dilute ethanoic acid.  $\times10^{-4}mol\:dm^{-3}$
3.Calculate the concentration of ethanoic acid in vinegar.  $\times10^{-3}mol\:dm^{-3}$
Important note: The section numbers mentioned in the video solution are specific to the 2024 syllabus.
You can refer to the question stem to find the section numbers in the 2025 syllabus.

  Lipoic acid is an antioxidant that can ltfyd+n7p;, s be taken as a supplement for the body.
1.Determine the empirical formula of lipoic acid.

Element	Percentage Composition by mass
C	46.56%
H	6.85%
O	15.5%
S	31.08%

C=  g, H=  g, O=  g, S=  g
2.Calculate the molar mass of the empirical formula of lipoic acid.  g $mol^{-1}$
3.If the actual molar mass of lipoic acid is 206.44g $mol^{-1}$, determine its molecular formula.  

  Potassium hydrogen phthalate or KHP * ybq+3l.sutz$(C_8H_5O_4K)$ is an acidic salt compound which is commonly used to standardize sodium hydroxide (NaOH) solutions. The reaction between KHP and NaOH is given below.
$KHC_8H_4O_4+NaOH$$\rightarrow$$KNaC_8H_4O_4$+$H^2O$
1.Calculate the mass of KHP needed to prepare $25.00cm^3$ of 0.100mol $dm^{-3}$ KHP solution.  g
2.Calculate the volume of $1.0mol\:dm^{-3}$ aqueous NaOH solution needed to prepare $50cm^3$ of 0.100mol $dm^{-3}$ aqueous NaOH solution.  $\times10^{-3}dm^3$
3.If 27.1 $cm^{3}$ of the KHP solution prepared in (a) were needed to standardize $25.0cm^3$ of the aqueous NaOH solution prepared in (b), calculate the exact concentration of the aqueous NaOH solution.  mol $dm^{-3}$

  Automobile airbags are inoqvgq3b(o0 8+u hcq9yflated with $N_2$, a byproduct of sodium azide decomposition, according to the following reaction.
$2NaN_{3(s)}\rightarrow2Na_{(s)}+3N_{2(g)}$
Calculate the mass (in grams) of sodium azide needed to generate $0.07m^3$ of $N_2$ at $1.01\times10^5 Pa$ and $26^{\circ}C$.mass of $NaN_3$=  g

  A sample of 9.70 g of an unknown organic compound composed of carbon, hydrog a:1xjane8 u*kjb dn64en, and nitrogen was burnt with excess oxygen. The combustion produced nitrogen gaj8a:x6 k*nnedab14jus,27.5 g of $CO_2$ and 6.57 g of $H_2O$.
1.Calculate the mass of nitrogen produced.$m_C$  , $m_H$  , $mN_N$=  
2.Determine the empirical formula of the compound.

  Siderite is a mineral containiil:tu*(m hh3by tc)0zng iron in the form of iron (II) carbonate,$FeCO_3 $.
A 15.00 g sample of impure siderite was ground into a fine powder and dissolved in $250.0cm^3$ of hot water, and then filtered to remove the insoluble components. After filtration, a $35.00 cm^3$ sample of the iron solution was analyzed via redox titration using a 0.120 $mol \ dm^{-3}$ solution of potassium dichromate. The balanced redox equation is given below:
$Cr_2O^{2-}_{7(aq)}+14^+_{(aq)}+6Fe^{2+}_{(aq)}\rightarrow2Cr^{3+}_{(aq)}+6Fe^{3+}_{(aq)}+7H_2O_{(l)}$
1. 1.Calculate the theoretical percent composition of iron in a sample of pure siderite or iron (II) carbonate.  %
2.If $18.1cm^3$ of dichromate solution is used to titrate the actual iron sample to the equivalence point, calculate the number of moles of iron in the titrated sample.  mol
3.Using your value from (ii), determine the mass of iron present in the original sample of siderite.  g
4.Using the experimental number of moles of $Fe^{2+}$ found in (ii), calculate the experimental mass of iron carbonate $(FeCO_3)$ in the impure sample and then calculate the percent of impurities found in this sample.Percent impurities  %
2.Another iron-containing mineral is a hydrate of iron sulfate,$Fe_x(SO_4)_y ⋅ n H_2O$, pure sample is first heated to drive off all of the water. After heating to a consistent mass, a sample with a mass of 5.250 g is found to have 3.561 g of anhydrous material remaining. The remaining anhydrous material was analyzed and found to have 36.76%,21.11% sulfur, and 42.13% oxygen.
1.Determine the empirical formula of the anhydrate.
2.If the molar mass of the hydrate is determined to be $151.92 gmol^{-1}$, what is the actual formula of the anhydrate?
3.Use the information given in part b(i) to determine the number of moles of water present and, thus, the formula of the hydrate.

  The elemental composition of compound B is givenc4 ;wf 6vue2eh in the table.

enskipElement	Percentage abundance by mass /%
C	75
H	25

What is the empirical formula of compound B?
Atomic masses (amu) C=12,H=1