Chemistry HELP??!!???

Question

I need help in chem. Please help! Thanks! :)

1) A liquid is allowed to evaporate and leaves no residue. Can you determine whether it was an element, a compound or a mixture?

2) Which of the following are substances?Which are mixtures?

a. ethanol

b. motor oil

c. vinegar

d. neon

3) If 44 grams of carbon dioxide react completely with 18 grams of water, what is the mass of carbonic acid formed?

Answer 1

Ok I did a biochemistry degree so some of these questions I can help you with, or at least eliminate the wrong answers

1- if it leaves no residue my guess is it's a compound only because you would filter a mixture to get a compound. i think that some elements can leave residue, so I'm pretty sure it's a compund.

2- neon and ethanol are substances - neon because it;s an element and ethanol because it's a basic carbon/OH compund, there's no multiple compounds there.

i don't know the formula for vinegar is. But wild guess - it's a substance.

3 - I don't know - biochem = no numbers

4- ammonia = nitrogen and hydrogen

Answer 2

1) it is either a compound or an element

2) subs = neon, ethanol, vinegar

3) CBB

4) nitrogen and 3 hydrogens

Answer 3

1) no, it could have been a mixture of compounds that all evaporate leaving no residue, it could have been a compound that evaporates to give no residue. Could have been an element.

2) ethanol and Neon are substances, they are pure compounds

motor oil is a mixture

vinegar is a dilute solution of acteic acid in water, so it is a mixture as well, water can be evaporated off thus changing the composition. The composition of a pure substance can not be altered by non-chemical processes

3) CO2 + H2O -----> H2CO3

1 mole of CO2 reacts with 1 moles of H2O to give 1 moles H2CO3. You need to work out how many moles of each that you started with, and form that you can work out moles of H2CO3 and then mass of H2CO3

moles= mass / molar mass

molar mass CO2 = 12 + (2x16) = 44 g/mol

molar mass H2O + (2 x 1) + 16 = 18 g/mol

moles CO2 = 44 g / 44 g/mol = 1 mole

moles H2O = 18g / 18 g/mol = 1 mole

Therefore 1 mole H2CO3 will be produced, because you have reacted 1 mole of each of the reactants.

mass H2CO3 = moles x molar mass

molar mass H2CO3 = (2 x 1) + 12 + (3 x 16) = 62 g/mol

mass H2CO3 = 1 x 62 g/mol

= 62 g H2CO3

4) Nitrogen (N) and Hydrogen (H)

Answer 4

1. no

2. substance: ethanol, vinegar, neon

3.you cannot get carbonic acid by mixing water with co2

4. 1 atom of nitrogen and 3 atoms hydrogen