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Solnce55 [7]
3 years ago
13

Which of the following measurements is expressed to three significant figures? 7.30 × 10–7 km 0.007 m 7077 mg 0.070 mm

Chemistry
1 answer:
Sonbull [250]3 years ago
4 0

7.30 x 10^-7 km. the others have 4 significant figures.

You might be interested in
Which of the following is a negatively charged particle?
kirza4 [7]

Answer:

B. electron

Explanation:

B. electron

electron is a negatively charged particle

proton is a positively charged particle

7 0
3 years ago
determine the ph of a buffer that is 0.55 M HNO2 and 0.75 M KNO2. tha value of Ka for HNO2 is 6.8*10^-4
Mariana [72]

Answer:

pH = 3.3

Explanation:

Buffer solutions minimize changes in pH when quantities of acid or base are added into the mix. The typical buffer composition is a weak electrolyte (wk acid or weak base) plus the salt of the weak electrolyte. On addition of acid or base to the buffer solution, the solution chemistry functions to remove the acid or base by reacting with the components of the buffer to shift the equilibrium of the weak electrolyte left or right to remove the excess hydronium ions or hydroxide ions is a way that results in very little change in pH of the system. One should note that buffer solutions do not prevent changes in pH but minimize changes in pH. If enough acid or base is added the buffer chemistry can be destroyed.

In this problem, the weak electrolyte is HNO₂(aq) and the salt is KNO₂(aq). In equation, the buffer solution is 0.55M HNO₂ ⇄ H⁺ + 0.75M KNO₂⁻ . The potassium ion is a spectator ion and does not enter into determination of the pH of the solution. The object is to determine the hydronium ion concentration (H⁺) and apply to the expression pH = -log[H⁺].

Solution using the I.C.E. table:

              HNO₂ ⇄    H⁺   +   KNO₂⁻

C(i)        0.55M       0M      0.75M

ΔC            -x            +x          +x

C(eq)  0.55M - x       x     0.75M + x    b/c [HNO₂] / Ka > 100, the x can be                                    

                                                             dropped giving ...

           ≅0.55M        x       ≅0.75M        

Ka = [H⁺][NO₂⁻]/[HNO₂] => [H⁺] = Ka · [HNO₂]/[NO₂⁻]

=> [H⁺] = 6.80x010⁻⁴(0.55) / (0.75) = 4.99 x 10⁻⁴M

pH = -log[H⁺] = -log(4.99 x 10⁻⁴) -(-3.3) = 3.3

Solution using the Henderson-Hasselbalch Equation:

pH = pKa + log[Base]/[Acid] = -log(Ka) + log[Base]/[Acid]

= -log(6.8 x 10⁻⁴) + log[(0.75M)/(0.55M)]

= -(-3.17) + 0.14 = 3.17 + 0.14 = 3.31 ≅ 3.3

3 0
3 years ago
A 13 g sample of P4010 contains how many
Alex777 [14]

Answer:

\large \boxed{5.5 \times 10^{22}\text{ molecules of P$_{2}$O}_{5}}

Explanation:

You must calculate the moles of P₄O₁₀, convert to moles of P₂O₅,  then convert to molecules of P₂O₅.

1. Moles of P₄O₁₀

\text{Moles of P$_{4}$O}_{10} = \text{13 g P$_{4}$O}_{10} \times \dfrac{\text{1 mol P$_{4}$O}_{10}}{\text{283.89 g P$_{4}$O}_{10}} = \text{0.0458 mol P$_{4}$O}_{10}

2. Moles of P₂O₅

P₄O₁₀ ⟶ 2P₂O₅

The molar ratio is 2 mol P₂O₅:1 mol P₄O₁₀

\text{Moles of P$_{2}$O}_{5} = \text{0.0458 mol P$_{4}$O}_{10} \times \dfrac{\text{2 mol P$_{2}$O}_{5}}{\text{1 mol P$_{4}$O}_{10}} = \text{0.0916 mol P$_{2}$O}_{5}

3. Molecules of P₂O₅

\text{No. of molecules} = \text{0.0916 mol P$_{2}$O}_{5} \times \dfrac{6.022 \times 10^{23}\text{ molecules P$_{2}$O}_{5}}{\text{1 mol P$_{2}$O}_{5}}\\\\= \mathbf{5.5 \times 10^{22}}\textbf{ molecules P$_{2}$O}_{5}\\\text{There are $\large \boxed{\mathbf{5.5 \times 10^{22}}\textbf{ molecules of P$_{2}$O}_{5}}$}

6 0
3 years ago
During normal, relaxed respiration, about 500ml of air enters and leaves the lungs with each respiratory cycle. this is called t
Marianna [84]

During normal respiration, about 500ml of air enters and leaves the lungs with each respiratory cycle. This is called the<u> tidal volume</u>.

When a person is relaxed, the normal amount of air such a person breathes in and out is called the tidal volume. It is usually measured in millimeters. For the average adult male, it is 500ml, and the tidal volume of average adult female 400ml.

In order to regulate oxygen intake and expulsion of carbon dioxide, the lungs act as buffers in order to absorb the maximum amount of oxygen possible for respiration and other metabolic functions in the body.

When the tidal volume is above or below the 500ml mark, it could signal the presence of underlying pathological conditions like bronchitis, emphysema and asthma.

To find out more about tidal volume, visit:

brainly.com/question/17439101

#SPJ4

6 0
1 year ago
Consider the gold isotope 197Au. How many electrons, protons, and neutrons are in a neutral 197Au atom?
tangare [24]

Answer:

The 197Au isotope has 79 protons, 79 electrons and 118 neutrons

Explanation:

Step 1: The isotope = 197Au

Step 2: Calculate neutrons, electrons and protons

197 = Number of protons + number of neutrons

Isotopes always have the same proton number ( is the same as the atomic number). For Gold (Au) is this 79.

The number of electrons is equal to the number of protons in a neutral atom. Since we have 79 protons, there are also 79 electrons.

All isotopes of Au have a different number of neutrons.

The number of neutrons = 197 -79 = 118 neutrons

The 197Au isotope has 79 protons, 79 electrons and 118 neutrons

6 0
3 years ago
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