Laura and 50ml of foil and water to 100 ml of ice water into a freezer what at what temperature will the water freeze

(Atomic masses used are C = 12.0 g mol–1, O = 16.0 g mol–1, H = 1.01 g mol–1, Cu = 63.5 g mol–1,)

alex41 [277]

Question 1

The formula mass of methanol is $12.0+3(1.01)+16.0+1.01=32.04$ g/mol.

Therefore, in 5.0 grams of methanol, there are $5.0/32.04=\boxed{0.16}$ moles.

Question 2

The formula mass of copper(II) carbonate is $63.5+12.0+3(16.0)=123.5$ g/mol.

This means that in 9.0 grams of copper(II) carbonate, there are $9.0/123.5=0.072874493927126$ moles.

Using Avogradro's number, there are $(0.072874493927126)(6.022 \times 10^{23})=\boxed{4.4 \times 10^{22}}$ molecules.

Question 3

The formula mass of cyclohexane is $12.0(6)+1.01(12)=84.12$ g/mol.

So, 3.0 grams of cyclohexane is the same as $3.0/84.12=\boxed{0.036}$ moles.

Question 4

The formula mass of benzene is $12.0(6)+1.01(6)=78.06$ g/mol.

This means that 4.00 moles of benzene has a mass of $(78.06)(4.00)=\boxed{312}$ grams.

Question 5

1000 atoms of calcium is the same as $\frac{1.000}{6.022 \times 10^{23}}$ moles.

This is equal to $\frac{1000}{6.022 \times 10^{23}} \cdot 40.078=\boxed{6.7 \times 10^{-20}}$ grams.

6 0

1 year ago

A flask contains 0.280 mol of liquid bromine, br2. Determine the number of bromine molecules present in the flask.

Nat2105 [25]

Answer:

1.68 × 10²³ Molecules

Explanation:

As we know that 1 mole of any substance contains exactly 6.022 × 10²³ particles which is also called as Avogadro's Number. So in order to calculate the number of particles (molecules) contained by 0.280 moles of Br₂, we will use following relation,

Moles = Number of Molecules ÷ 6.022 × 10²³ Molecules.mol⁻¹

Solving for Number of Molecules,

Number of Molecules = Moles × 6.022 × 10²³ Molecules.mol⁻¹

Putting values,

Number of Molecules = 0.280 mol × 6.022 × 10²³ Molecules.mol⁻¹

Number of Molecules = 1.68 × 10²³ Molecules

Hence,

There are 1.68 × 10²³ Molecules present in 0.280 moles of Br₂.

4 0

2 years ago

What is the percentage of nitrogen, by mass, in calcium nitrate?.

SCORPION-xisa [38]

Answer:

Nitrogen = 17.07%

Explanation:

We are asked to calculate the percentage by mass of nitrogen in Ca(NO3)2.

The molar mass of calcium nitrate is 164,088 g/mol.

In this 164.088 g/mol there are 2 nitrogen atoms.

Molar mass of nitrogen = 14,0067 g/mol

% Nitrogen = molar mass of N/total molar mass of the compound

% Nitrogen =[(2 x 14.0067)/164.088]*100

% Nitrogen = 17.07%

Please mark me as brainliest if you found this answer helpful

7 0

2 years ago

For each of the following circumstances, indicate whether the calculated molarity of NaOH would be lower, higher or unaffected.

irina [24]

Answer:

a)calculated molarity of NaOH would be lower

b) calculated molarity of NaOH would be lower

c) calculated molarity of NaOH would be lower

d) calculated molarity of NaOH would be unaffected

Explanation:

Let us recall that the reaction of NaOH and HCl is as follows;

NaOH(aq) + HCl(aq) ----> NaCl(aq) + H2O(l)

Since the reaction is 1:1, when the number of moles of HCl reacting with NaOH is low due to dilution, the calculated molarity of NaOH also becomes less than it's accurate value.

When 40mL of water is added to the titration flask rather than 25ml of water, the acid is more dilute hence less number of moles of acid than necessary reacts with the base thereby yielding a less than accurate value of the molarity of NaOH.

If the burette wet with water is not rinsed with NaOH solution, the concentration of the NaOH in the burette decreases due to dilution with water and a less than accuracy value is calculated for the molarity of NaOH.

If five drops of phenolphthalein is used instead of one or two drops, there is no qualms since enough phenolphthalein may be added to ensure that a sharp end point is obtained.

8 0

3 years ago

The salts NaCl and CaCl

Irina18 [472]

The answer is 8 :)
All nobel gases have 8 outer electrons.

6 0

3 years ago