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3 years ago

Please help with at least one of these questions! I have about 15-20 mins left :(

Chemistry

1 answer:

aksik [14]3 years ago

6 0

Answer:

1. Melting ice does not change the composition of the water or ice, as the ice is only changing its state from solid to liquid. Boiling water also does not change the composition of the water or gas, as the water is only changing its state from liquid to gas.

2. Burning paper turns the paper fibres to ashes. Making yoghurt from milk is making something new out from milk, where there is fermentation going on to turn the lactose into an acid, resulting in a chemical change and not a physical change.

Explanation:

A chemical change is when a new substance is formed from the old thing due to a chemical process such as burning where energy is given off or absorbed, while a physical change is basically changing the state of a substance but its composition does not change, unlike a chemical change.

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For the reaction 2 HCl + Na2CO3 → 2 NaCl + H2O + CO2 8.0 moles of CO2 is collected at STP. What is the volume of CO2? 1. 57.6 L

Dmitry [639]

Answer:

Option 5. 179L

Explanation:

The reaction is:

2 HCl + Na₂CO₃ → 2NaCl + H₂O + CO₂

The amount of collected CO₂ is 8 moles.

We apply the Ideal Gases Law at STP

STP are 1 atm of pressure and 273K of T°

P . V = n . R . T

1atm . V = 8 mol .0.082L.atm/mol.K . 273K

V = (8 mol .0.082L.atm/mol.K . 273K) / 1 atm = 179 L

6 0

4 years ago

What happens to the atoms in food once animals eat them?

deff fn [24]

Answer:

i think

they are used to male the animal grow

8 0

2 years ago

The height of a column of mercury in a closed-end manometer is 13.2 cm. What is the pressure of the gas in torr

AlladinOne [14]

Answer:

$P_{gas}=131.96torr$

Explanation:

Helo,

In this case, the pressure must be computed as follows:

$P_{gas}=gh\rho _{Hg}$

Which is using the density of mercury (13.6 g/mL) and its height, thus, we obtain (using the proper units):

$P_{gas}=9.8\frac{m}{s^2}*(13.2cm *\frac{1m}{100cm} )*(13.6\frac{g}{cm^3}*\frac{1kg}{1000g}*\frac{1x10^6cm^3}{1m^3} )\\\\P_{gas}=17592.96Pa*\frac{760torr}{101325Pa} \\\\P_{gas}=131.96torr$

Best regards.

5 0

3 years ago

Calculate the pH of a 0.50 M HIO. The Ka of hypoiodic acid, HIO, is 2.3x10–11.0.305.325.479.474.80

never [62]

Answer:

pH = 5.47

Explanation:

The equilibrium that takes place is:

HIO ↔ H⁺ + IO⁻

Ka = $\frac{[H+][IO-]}{[HIO]}$ = 2.3 * 10⁻¹¹

At equilibrium:

[HIO] = 0.5 M - x

[H⁺] = x

[IO⁻] = x

Replacing those values in the equation for Ka and solving for x:

$Ka=\frac{x^2}{0.5-x}=2.3*10^{-11} \\x^2=(2.3*10^{-11})(0.5-x)\\x^2=1.15*10^{-11}-2.3*10^{-11}x\\x^2+2.3*10^{-11}x-1.15*10^{-11}=0\\x=3.39*10^{-6}$

Then [H⁺]=3.39 * 10⁻⁶, thus pH = 5.47

7 0

3 years ago

Sodium hydroxide reacts with aluminum and water to produce hydrogen gas: 2 Al(s) + 2 NaOH(aq) + 6 H2O(l) → 2 NaAl(OH)4(aq) + 3 H

lianna [129]

Answer:

The mass of hydrogen gas formed is 0.205 grams

Explanation:

Step 1: Data given

Mass of 1.83 grams of Al

Mass of NaOH = 4.30 grams

Molar mass of Al = 26.98 g/mol

Molar mass of NaOH = 40 g/mol

Step 2: The balanced equation:

2 Al(s) + 2 NaOH(aq) + 6 H2O(l) → 2 NaAl(OH)4(aq) + 3 H2(g)

Step 3: Calculate moles of Al

Moles Al = mass Al / Molar mass Al

Moles Al = 1.83 grams / 26.98 g/mol

Moles Al = 0.0678 moles

Step 4: Calculate moles of NaOH

Moles NaOH = 4.30 grams / 40 g/mol

Moles NaOH = 0.1075 moles

Step 5: Calculate limiting reactant

For 2 moles of Al, we need 2 moles of NaOH

Aluminium is the limiting reactant. It will completely be consumed ( 0.0678 moles)

NaOH is in excess. There will react 0.0678 moles

There will remain 0.1075 - 0.0678 = 0.0397 moles

Step 6: Calculate moles of hydrogen

For 2 moles of Al, we need 2 moles of NaOH, to produce 3 moles of hydrogen

For 0.0678 moles of Al, there is produced 0.0678 *3/2 = 0.1017 moles of H2

Step 7: Calculate mass of H2

Mass of H2 = Moles H2 * Molar mass of H2

Mass of H2 = 0.1017 moles * 2.02 g/mol

Mass of H2 = 0.205 grams

The mass of hydrogen gas formed is 0.205 grams

6 0

3 years ago