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dalvyx [7]
2 years ago
7

Best answer and explanation will get marked brainiest

Chemistry
1 answer:
Darina [25.2K]2 years ago
4 0

The number 345,000 has 3 significant figures because the trailing zeros are not significant since there's no decimal point.

<h3>What is significant figures?</h3>

Significant figures of a number in positional notation are digits in the number that are reliable and necessary to indicate the quantity of something.

Also significant figures can be defined as, the number of digits in a value, often a measurement, that contribute to the degree of accuracy of the value.

Examples of significant figures;

  • 405 = 3 significant figures
  • 405000 = 3 significant
  • 0.040500 = 5 significant figures

<u>Note:</u> leading zeros are not significant but trailing zeros, which are zeros at the end of a number, are significant only if the number has a decimal point.

345,000 = 3.45 x 10⁵ (3 significant figures)

Thus, the number 345,000 has 3 significant figures because the trailing zeros are not significant since there's no decimal point.

Learn more about significant figures here: brainly.com/question/24491627

#SPJ1

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4. When 1.00 L of 1.00 M Ba(NO3)2 solution at 25.0˚C is mixed with 1.00 L of 1.00 M Na2SO4 solution at 25.0˚C in a calorimeter,
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Answer:

The final temperature of the mixture is 28.11 °C

Explanation:

Step 1: Data given

Volume of 1.00 M Ba(NO3)2 = 1.00 L

Temperature = 25.0 °C

Volume of 1.00 M Na2SO4 = 1.00 L

enthalpy change is – 26 kJ per mol BaSO4

The specific heat of water is 4.18 J/g ·˚C

the density of water is 1.00 g/mL

Step 2: The balanced equation

Ba(NO3)2(aq) + Na2SO4(aq) → 2NaNO3(aq) + BaSO4(s)

Step 3: Calculate the total volume

Total volume = 1.00 L + 1.00 L = 2.00 L = 2000 mL

Step 4: Calculate mass

Mass = volume * density

Mass = 2000 mL * 1g/mL

Mass = 2000 grams

Step 5: Calculate moles BaSO4 formed

For 1 mol Ba(NO3)2 we need 1 mol Na2SO4 to produce 1 mol BaSO4

There is no limiting reactant, both Ba(NO3)2 and Na2SO4 will be completely be consumed (1 mol). We'll have 1.0 mol of BaSO4 produced.

Step 6: Calculate Q

Q = - ΔH

ΔH is negative so the reaction is exothermic, what means the temperature increases

Q is always positive, so Q = 26kJ = 26000 J

Step 6: Calculate the heat transfer

Q= m*c*ΔT

⇒with Q = the heat transfer = TO BE DETERMINED

⇒with m =the mass of the solution = 2000 grams

⇒with c= the specific heat of the solution = 4.18 J/g°C

⇒with ΔT = the change of temperature = T2 - T1 = T2 - 25.0

26000 = 2000 * 4.18 * (T2 - 25.0 °C)

3.11 = T2 - 25.0 °C

T2 = 25.0 + 3.11 °C

T2 = 28.11 °C

The final temperature of the mixture is 28.11 °C

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An unknown amount of mercury (II) oxide was decomposed in the lab. Mercury metal was formed and 5.20 L of oxygen was released at
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Answer:

  • <u>68.3g</u>

Explanation:

<u>1. Word equation:</u>

  • <em>mercury(II) oxide → mercury + oxygen </em>

<u>2. Balanced molecular equation:</u>

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<u>3. Mole ratio</u>

Write the ratio of the coefficients of the substances that are object of the problem:

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<u>4. Calculate the number of moles of O₂(g)</u>

Use the equation for ideal gases:

          pV=nRT\\\\\\n=\dfrac{pV}{RT}\\\\\\n=\dfrac{0.970atm\times5.20L}{0.08206atm.L/K.mol\times 390.0K}\\\\\\n=0.1576mol

<u>5. Calculate the number of moles of HgO</u>

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<u>6. Convert to mass</u>

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  • molar mass of HgO: 216.591g/mol

  • mass = 0.315mol × 216.591g/mol = 68.3g

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