Question 3 The moles of sulfate in 250 ml, 6 M Na2504 is 1.5 Question 4 The form

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Question 3 The moles of sulfate in 250 ml, 6 M Na2504 is 1.5 Question 4 The formula for the compound formed between aluminum ions and phosphate ions is OAl3(PO4)3 AIPO4 Al2(PO4)3 AIP Question 5 Which species has 54 electrons 132 xe 54 12 Te2- 52 ? 118Sn2. 50 O 112ca 48 O 132xe2. 54 Question 6 Of the following gases the bne with the greatest density at STP is O Ne O NH3 He Question 7 What volume (mL) of 7.48 x 10-2 M perchloric acid can be neutralized with 115 mL of 0.244 M sodium hydroxide? 125 ?. 8.60 188 750 375

Explanation / Answer

Answer – Q 3) We are given volume of sodium sulfate Na2SO4 = 250 mL

molarity of sodium sulfate [Na2SO4] = 6 M

We need to calculate the moles of sulfate ion mean SO42-

We need to first calculate the moles of Na2SO4

We know formula

Molarity = moles / volume (L)

So, moles = molarity x volume (L)

                 = 6 M x 0.250 L

                 = 1.5 moles

In 1 moles of Na2SO4 there are 2 moles of sodium (Na+) ion and 1 moles of sulfate ion (SO42-)

So,

1 moles of Na2SO4 = 1 moles of SO42-

So, 1.5 moles of Na2SO4 = ? moles of SO42-

= 1.5 moles of SO42-

So, 1.5 moles of sulfate in 250 mL of 6 M Na2SO4 solution.

Q 4) We are given aluminum ion and phosphate ion

We know aluminum ion has charge 3+ (Al3+), since it is in III A group and phosphate is polyatomic ion with charge 3- (PO43-)

Now we need to balance the charge for forming the compound. Both aluminum and phosphate ions have same number of cation and anion.

so compound formula is AlPO4

Q 5) We are given 54 electrons and need to find out the species.

We know for neutral species atomic number = electron number

In 54132 Xe+ there are 53 electrons, since there is +1 charge and its atomic number is 54, so total number of electrons are 54-1 = 53

In 52128 Te2- there are 54 electrons, since there is -2 charge and its atomic number is 52, so total number of electrons are 52 +2 = 54

So, species 52128 Te2- has 54 electrons.

Q 6) We know density is the ratio of mass by volume. At STP 1 moles of gas is 22.4 L volume , so we know volume at STP and it is fix for all gas at STP.

Now we know density is directly proportional to mass. Higher mass has higher density at STP, so we need to see for molar mass of each given gases.

CH4 has 16 g, Ne has 20.180 g , NH3 has 17.01 g and He has 4.00 g

So Ne has highest mass out of given gases and density of Ne has is highest at STP.

Q 7) We are given, molarity of perchloric acid = 7.48 x 10-2 M ,

Molarity of sodium hydroxide NaOH = 0.244 M , volume of NaOH = 115 mL

We know reaction between perchloric acid and sodium hydroxide

HClO4 + NaOH ----> NaClO4 + H2O

Now we need to calculate moles of NaOH first

Moles of NaOH = 0.244 M x 0.115 L

                          = 0.0378 moles of NaOH

From the balanced reaction

1 moles of NaOH = 1 moles of HClO4

So, 0.0281 moles of NaOH = ?

= 0.0281 moles of HClO4

Now volume of HClO4 = 0.0281 moles / 7.48 x 10-2 M

                                     = 0.375 L

So, volume of HClO4 = 375 mL

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