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kompoz [17]
3 years ago
12

Why does a microscope stage have a small hole in it?

Chemistry
1 answer:
jarptica [38.1K]3 years ago
4 0
Answer: B. Allow light to pass through. :)
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Which of the following will occur when a solution of Pb(NO3)2(aq) is mixed with a solution of KI(aq)?
inna [77]

When a solution of Pb(NO3)2(aq) is mixed with a solution of KI(aq), a precipitate of PbI₂ will form; K⁺ and NO₃⁻ are spectator ions.

<u>Explanation:</u>

When an aqueous solution of lead nitrate (Pb(NO₃)₂ is mixed with aqueous solution of potassium iodide (KI), then there is a precipitate formation of lead iodide (PbI₂), and the potassium  (K⁺) ion and nitrate (NO₃⁻) ion acts as spectator ions that is ions do not involved in the reaction.

The reaction can be represented as,

Pb(NO₃)₂(aq) + 2 KI (aq) → PbI₂(s) + 2KNO₃(aq)

The ionic equation can be written as,

Pb²⁺(aq) + 2 NO₃⁻(aq) + 2 K⁺(aq) + 2 I⁻(aq) →  PbI₂(s) + 2K⁺(aq) + 2NO₃⁻(aq)

On both sides of the equation, we have K⁺ and NO₃⁻ ions, which gets cancelled, and these 2 ions are called as spectator ions.

3 0
3 years ago
How many moles are there in 40g of calcium
drek231 [11]
40 grams ÷ 40.08 grams/moles = 1 mole
8 0
3 years ago
What is the density of a substance with a mass of 15.0 g and a volume of 5.0 mL?
Vinvika [58]

Answer:

B. 3.0 g/ml

Explanation:

density formula: mass/volume

15/5=3

5 0
3 years ago
A sample of O2 gas (2.0 mmol) effused through a pinhole in 5.0 s. It will take __________ s for the same amount of CO2 to effuse
ludmilkaskok [199]

Answer:

\large \boxed{\text{5.9 s}}

Explanation:

Graham’s Law applies to the effusion of gases:

The rate of effusion (r) of a gas is inversely proportional to the square root of its molar mass (M).

r \propto \dfrac{1}{\sqrt{M}}

If you have two gases, the ratio of their rates of effusion is

\dfrac{r_{2}}{r_{1}} = \sqrt{\dfrac{M_{1}}{M_{2}}}

The time for diffusion is inversely proportional to the rate.

\dfrac{t_{2}}{t_{1}} = \sqrt{\dfrac{M_{2}}{M_{1}}}

Let CO₂ be Gas 1 and O₂ be Gas 2

Data:

M₁ = 44.01

M₂ = 32.00

Calculation

\begin{array}{rcl}\dfrac{t_{2}}{t_{1}} & = & \sqrt{\dfrac{M_{2}}{M_{1}}}\\\\\dfrac{t_{2}}{\text{5 s}}& = & \sqrt{\dfrac{44.01}{32.00}}\\\\& = & \sqrt{1.375}\\t_{2}& = & \text{5 s}\times 1.173\\& = & \mathbf{5.9 s} \\\end{array}\\\text{It will take $\large \boxed{\textbf{5.9 s}}$ for the carbon dioxide to effuse.}

4 0
3 years ago
A chemist prepares a solution of sodium chloride by measuring out 25.4 grams of sodium chloride into a 100. mL volumetric flask
mr_godi [17]

Answer:

The concentration in mol/L =  4.342 mol/L

Explanation:

Given that :

mass of sodium chloride = 25.4 grams

Volume of the volumetric flask = 100 mL

We all know that the molar mass of sodium chloride NaCl = 58.5 g/mol

and number of moles = mass/molar mass

The number of moles of sodium chloride = 25.4 g/58.5 g/mol

The number of moles of sodium chloride = 0.434188 mol

The concentration in mol/L = number of mol/ volume of the solution

The concentration in mol/L = 0.434188 mol/ 100 × 10⁻³ L

The concentration in mol/L =  4.34188 mol/L

The concentration in mol/L =  4.342 mol/L

5 0
3 years ago
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