Please help and thank you so much

What does it mean to be an exothermic chemical reaction? a) Energy is released when no new substances are made. b) Energy is rel

mario62 [17]

Answer:b

Explanation:

Energy is released to form the product

3 0

3 years ago

The mole is defined as the amount of a substance containing the same number of particles as exactly 12 g of C-12. The amu is def

Pavlova-9 [17]

Answer:

Because it wouldn't make any sense

Explanation:

First of all, I think it's important to highlight the definition of isotope.

Isotope (Wikipedia): Variants of a particular chemical element <u>which differ in neutron number</u>...

This means that two isotopes are the same element but have different net mass per atom, due to the different number of neutrons.

Therefore, it's important to make the definition on the same isotope so that the proportion is equal. If the definition would be made on different isotopes, the proportion wouldn't have any sense. Let me be clear with this example:

mass in grams of a C-12 atom = 1.9944235 × 10 ^ -23 g --> this is the mass of a single C atom.

By definition --> 1 mol of anything = 6.02 x 10 ^ 23 particles of anything

Therefore, we know how much a single C atom weights. How many grams do you think that 6.02 x 10 ^ 23 atoms of C (i.e a mol of C) could weight??

1 single C atom ----------------------------- 1.9944235 × 10 ^ -23 g

6.02 x 10 ^ 23 atoms of C ------------ <u>12.006 g !!</u>

These 12 g is the same quantity than above! Therefore, 1 mol of C weights 12 g. If the definition were made with 13 g of C-13 (the other C isotope), these numbers will not be the same --> There would be a contradiction.

Regarding the second question, we need to search Ne-20 atomic mass in grams --> 3,3509177 × 10 ^ -23 g

Hence, if we follow the same rule, the amu would be 1/12 of Ne-20.

[ 3,3509177 × 10 ^ -23 g ] / 12 = 2.79 ^ -24 g

3 0

3 years ago

Is h2c2o4 an Arrhenius base or arrhenius acid

maksim [4K]

Answer:
Oxalic Acid is and Arrhenius Acid.

Explanation:
According to Arrhenius Theory of acid and base, "Acid is any substance which when dissolved in water produces H⁺ Ions".

Therefore, Oxalic Acid is a diprotic substance, which is capable of donating protons in water. This acidity of oxalic acid can be dedicated to the stability of conjugate base, this stability comes from resonance of the negative charges on Oxalate ion. Below reaction shows the dissociation of Oxalic Acid into Protons and Oxalate Ion.

6 0

3 years ago

An unknown substance is obtained by police. The forensics laboratory has

timurjin [86]

Answer:

70.0 %

Explanation:

Step 1: Given data

Mass of nitrogen (mN): 74.66 g

Mass of the compound (mNxOy): 250 g

Step 2: Calculate the mass of oxygen (mO) in the compound

The mass of the compound is equal to the sum of the masses of the elements that form it.

mNxOy = mN + mO

mO = mNxOy - mN

mO = 250 g - 74.66 g = 175 g

Step 3: Determine the percent composition of oxygen in the sample

We will use the following expression.

%O = mO / mNxOy × 100%

%O = 175 g / 250 g × 100% = 70.0 %

5 0

3 years ago

Does anybody know how to do q4. Please show working out thanks.

insens350 [35]

Answer:

% purity of limestone = 96.53%

Explanation:

Question (4).

Weight of impure CaCO₃ = 25.9 g

Molecular weight of CaCO₃ = 40 + 12 + 3(16)

= 100 g per mole

We know at S.T.P. number of moles of CO₂ = 1 and volume = 22.4 liters

From the given reaction, 1 mole of CaCO₃ reacts with 1 mole or 22.4 liters of

CO₂.

∵ 22.4 liters of CO₂ was produced from CaCO3 = 100 g

∴ 1 liter of CO₂ will be produced by CaCO₃ = $\frac{100}{22.4}$

∴ 5.6 liters of CO₂ will be produced by CaCO₃ = $\frac{100\times 5.6}{22.4}$

= 25 g

Therefore, % purity of CaCO₃ = $\frac{\text{Weight calculated}}{{\text{Weight given}}}\times 100$

= $\frac{25}{25.9}\times 100$

= 96.53 %

7 0

3 years ago