# Some desperate chem help

2
a) Calculate the expected mass of one mole of 31^P atoms that the avogadro constant equals 6.0225 x10^23, the mass of one electron equals 9.1091x10^-28g, the mass of one proton equals 1.6725x10^-24g and the mass of one nuetron equals 1.6748x10^-24g.

b) The actual mass of one mole of 31^P atoms is 30.9738g. Try to account for the difference between this valueand your answer in (a).

3.
A mixture of MGS04 and CuSO4.7H20 is heated at 120(degrees C) until a mixture of the anhydrous compounds is produced. If 5.00g of the mixture gave 3.00g of the anhydrous compounds, calculate the percentage by mass of MGSO4.7H20 in the mixture.

4.
1 mole of a hydrocarbon formula CnH2n was burned completely in oxygen producing carbon dioxide and water vapour only. It requires 192g of oxygen. Work out the formula of the hydrocarbon.

5. When 15cm^3 of gaseous hydrocarbon was exploded with 60cm^3 of oxygen (an XS), the final volume was 45cm^3. This decreased by 15cm^3 on treatment with NaOH solution ( removes C02 ). What was the formula of the hydrocarbon (all measuremnets were made at room temp. and pressure, & water produced is liquid)

6.
A fertilser contains ammonuim sulphate and pottasuim sulphate. A samply of 1.455g of the fertilise was warmed with 25cm^3, 0.2moddm^-3 NaOH solution giving of ammonia gas. The remaining NaOH that was not used requireed 28.7cm^3 of 0.100moldm^-3 HCl acid for nuetrulisation. Calculate the % by mass of ammonuim sulphate in the sample

I HAVE NO IDEA HOW TO DO ANY OF THESE PLEASE HELP ME I HAVE UNTIL FRIDAY :surprised

iansmith
Staff Emeritus
Gold Member
Can you show of the work/thinking/reasonning you have done on these problems. People will point out the errors and they help you solve your problem.

We are here to help but we are not here to do your homework.

Hint; in the first question all three particle masses are incorrect, some by small amount, some large.

The others; you have some digging to do.

sorry i now done 2ab and no. 5

3-
no real working outs because all i cud figure out that 2g of water had been extracted.

6-
I "think" its all a 1-1 ratio equation, so i found out moles of NaOH but then couldnt find mass because i dont no a; if the equation is balance b;the Mr of the ammonuim sulphate.

5-
I tried to use the pv=nrt forumula to work out the ammount of moles used, after that i was lost on wat to do