Answer:
2.04×10⁻⁴ moles of Ar
Explanation:
We begin from this knowledge:
1 mol of substance has 6.02×10²³ particles
Let's solve this by a rule of three:
6.02×10²³ atoms are contained in 1 mol of Ar
1.23×10²⁰ atoms must be contained in (1.23×10²⁰ . 1) / 6.02×10²³ =
2.04×10⁻⁴ moles of Ar
Mass of calcium carbonate (in grams) can be dissolved by 4.1 g of Hcl is 5.62g.
<h3>What is balanced equation?</h3>
A balanced equation is one for a chemical reaction in which the overall charge and the number of atoms for each component are the same for both the reactants and the products. In other words, the mass and charge of both sides of the reaction are equal.
The reaction between calcium carbonate and hydrochloric acid can be expressed through the chemical reaction,
CaCO₃ + 2HCl --> CaCl₂ + H₂O + CO₂
Hydrochloric acid has a molecular weight of 36.45 g/mol compared to calcium carbonate's molecular weight of 100 g/mol. According to the equation above, 72.9 g of hydrochloric acid may dissolve 100 g of calcium carbonate.
x = (4.1 g HCl)(100 g CaCO3 / 72.9 HCl)
x = 5.62 g.
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Answer:
1 g
Explanation:
From the formula;
N/No = (1/2)^t/t1/2
Where;
N= mass of radioactive element left after a time t = the unknown
No= mass of radioactive element originally present in the sample = 8g
t= time taken for N mass of the sample to remain = 1500
t1/2= half-life of the radioactive element = 500 years
Substituting values, we have;
N/8 = (1/2)^1500/500
N/8 = (1/2)^3
N/8 = 1/8
N= 1/8 ×8
N= 1 g
Therefore; mass of radioactive element left after 1500 years is 1 g
Answer:
You have to add 285.642 mL of KH2PO4
Explanation:
<u>Step 1:</u> What is a buffer
A buffer is a mixture of a weak acid and its conjugate base or a weak base and its conjugate acid. Buffers work by reacting with any added acid or base to control the pH.
pH of a buffer = pKa + log [conj base] / [weak acid]
<u>Step 2:</u> The ph of the buffer
6.97 = 7.21 =log [K2HPO4] / [KH2PO4]
-0.24 = log [K2HPO4] / [KH2PO4]
10 ^ -0.24 = [K2HPO4] / [KH2PO4] = 0.5754
0.5754 = (0.450 - x) / x
0.5754x = 0.450 - x
1.5754x = 0.450 L
x = 0.28564 = volume of KH2PO4
0.450 - 0.28564 = 0.16436 L K2HPO4
You have to add 285.642 mL of KH2PO4
Answer:
1) chewing breaks food into smaller pieces.
Explanation:
Chewing food changes the <u><em>PHYSICAL </em></u>appearance. The sugars in the other possible answer will completely change the composition of the food. So therefore, chewing breaks food into smaller pieces, is correct.
