2,000 students pay for online tutoring from india
1) true 2) false
3) not stated
2. for online tutoring, teachers and students must
1) be linked to the internet
2) have a voice-over connection with a headset
3) have digital pencils and writing pads
3. an hour of online tutoring from india
11) costs about $2.50 2) is about as expensive as a cup of coffee
$100
3) costs about
4.indian online tutors
1) don't all have university degrees
2) mustn't have an accent
3) learn about us education
5. tutors learn about british english to make them more easily understood by
beginners in the west.
1)true
2) false
3) not stated
6. what are benefits for online tutors in india?
1) they learn a lot 2) they work part time
3) they are well paid
n(MgO)=20/40=0.5моль
n(H3PO4)=49/98=0.5моль
По уравнению :
0.5-Х
3-2
Х=0.5*2/3=0.33моль (H3PO4)-необходимо на оксид магния ,т.е. кислота в избытке
20г(Mg)-Xг(Mg3(PO4)2)
72г(Mg)-262г(Mg3(PO4)2)
X=20*262/72=72,8г (Mg3(PO4)2)
Номер2
Al2(SO4)3+6KOH=3K2SO4+2Al(OH3)
n(Al2(SO4)3)=34,2/342=0.1моль
n(KOH)=14/56=0.25моль
По уравнению :
0.1-Х
1-6
Х=0.1*6=0.6моль (KOH)-приходится на сульфат алюминия ,т.е. КОН - в недостатке
14г(КОН)-Xг(Al(OH)3)
56г(КОН)-78г(Al(OH)3)
X=14*78/56=19.5г (Al(OH)3)