I don’t understand these questions please help

Explanation:

#3 Here basically you have to convert the mg to g first because we want to know the number of g of calcium per glass. That comes out to be 305/1000= 0.305g. So then, now you have to set up a algebraic equation

0.305x=1.3 (basically x refers to number of glasses)

x= 4.26 (now we know the kid needs to drink about 4 glasses/cups per day)

#4

Here convert moles to grams using molar mass of NaCl.

12.5molesx58.44g/mol > 730.5g NaCl

#5

So any gas at STP occupies 22.4 liters/1mol of gas.

110L x 1mol/22.4L = 4.91 moles N2

#6

So here basically do the same thing as 5 to find the moles. Then multiply that moles with 6.022x10^23 molecules (because 1 mol has 6.022x10^23 molecules) to find the number of molecules.

You should get 1.21x10^25 molecules

#7

Here basically find the moles first then convert the moles to grams using molar mass of H3PO4.

Molarity=moles/volume

1.7= x/0.550 (here we converted ml to L because volume is in liters for molarity)

x= 0.935 moles

Then, 0.935mol x 97.994g/1mol = 91.6g H3PO4

#8

Here convert the grams to moles using molar mass first (divide the grams by the molar mass) then multiply the number which is moles by 6.022x10^23 molecules (because 1 mol has 6.022x10^23 molecules) to find the number of molecules.

You should get 2.77x10^24 molecules

Hopefully everything makes sense lmk if it doesn't...I have tried my best to do these quickly I am sorry for any errors.

african americans demonstrated their newly found freedom by relocating often in search of relatives whom they had been separated from during slavery. others established schools to educate freed people and they built institutions such as churches and political organizations to advocate for their rights.

answer: you could do some invislibe ink.

explanation: i will tell you how to if u answer my question.